In (Figure 1), what is the current in the wire to the right of the junction? Suppose that ΔV = 2 V.

Mastering Physics Solutions Chapter 21 Electric current and Directly-Current Circuits

Mastering Physics Solutions

Chapter 21 Electric Current and Straight-Current Circuits Q.1CQ
What is the management of the electric current produced by an electron that falls toward the ground?
Solution:
By convention, the management of electric electric current is always in the contrary direction to the motion of negative charge. If the electron falls toward the ground. then the direction of current is in the upwardly direction

Chapter 21 Electric Electric current and Direct-Current Circuits Q.1P
How many coulombs of charge are in 1 ampere-hour?
Solution:

Chapter 21 Electric Current and Direct-Electric current Circuits Q.2CQ
Your body is composed of electric charges Does it follow, then, that you produce an electrical current when you lot walk?
Solution:
No An electrical current ¡due south proc1ucei when a internet charge mores Your trunk is electrically neutral, so no current is produced when you walk

Chapter 21 Electric Electric current and Direct-Current Circuits Q.2P
A flashlight bulb carries a current of 0.18 A for 78 s. How much charge flows through the bulb in this time? How many electrons?
Solution:

Chapter 21 Electric Electric current and Direct-Current Circuits Q.3CQ
Suppose y'all accuse a comb by rubbing information technology through your hair Practise you produce a electric current when you lot walk across the room conveying the comb?
Solution:
No.
By rubbing the comb through your hair you accept transferred charge from your pilus to the comb but the cyberspace accuse of you and the comb together is still zero Therefore no current is produced when you walk beyond the room carrying the comb

Affiliate 21 Electric Current and Direct-Current Circuits Q.3P
The flick tube in a item goggle box draws a current of 15 A. How many electrons strike the viewing screen every second?
Solution:

Chapter 21 Electric Current and Direct-Current Circuits Q.4CQ
Suppose you charge a comb by rubbing t through the fur on your dog'south back Do you lot produce a electric current when you walk across the room carrying the comb?
Solution:
Yes
At that place is a net accuse separated and deposited on the comb surface and by moving the rummage one identify to another you have created an current

Chapter 21 Electrical Current and Straight-Current Circuits Q.4P
IP A car battery does 260 J of work on the charge passing through it every bit it starts an engine,
(a) If the emf of the bombardment is 12 V, how much accuse passes through the bombardment during the start?
(b) If the emf is doubled to 24 V, does the amoun,t of charge passing through the bombardment increase or subtract? By what factor?
Solution:

Affiliate 21 Electric Current and Direct-Current Circuits Q.5CQ
An electron moving through a wire has an average drift speed that is very small Does this hateful that its instantaneous velocity is as well very small?
Solution:
No.
An electron may accept a fairly large instant velocity at whatsoever given time Simply considering its management of motion keeps changing due to its collisions with atoms in the wire its average velocity in particular direction is virtually very very minor.

Affiliate 21 Electric Current and Directly-Electric current Circuits Q.5P
Highly sensitive ammeters can mensurate currents as modest every bit 10.0 fA. How many electrons per second flow through a wire with a 10.0-fA current?
Solution:

Chapter 21 Electric Electric current and Direct-Current Circuits Q.6CQ
Arc automobile headlights connected in series or parallel? Requite an everyday observation that supports your answer
Solution:
Car head lights are wired in parallel every bit we can tell past the fact that some care has only one working caput light.

Chapter 21 Electrical Electric current and Straight-Current Circuits Q.6P
A goggle box connected to a 120-V outlet consumes 78 W of power, (a) How much electric current flows through the idiot box? (b) How long does it accept for ten meg electrons to pass through the TV?
Solution:

Chapter 21 Electric Current and Directly-Current Circuits Q.7CQ
Give an case of how four resistors of resistance R can be combined to produce an equivalent resistance of R.
Solution:

Chapter 21 Electric Current and Direct-Current Circuits Q.7P
BIO Pacemaker Batteries Pacemakers designed for longterm use usually employ a lithium-iodine battery capable of
supplying 0.42 A · h of charge,
(a) How many coulombs of charge can such a battery supply?
(b) If the boilerplate current produced by the pacemaker is 5.half-dozen μ A, what is the expected lifetime of the device?
Solution:

Chapter 21 Electric current and Direct-Current Circuits Q.8CQ
Is it possible to connect a grouping of resistors of value R in such a way that the equivalent resistance is less than R? If and then, give a specific example.
Solution:

Chapter 21 Electric Current and Direct-Current Circuits Q.8P
CE A conducting wire is quadrupled in length and tripled in diameter,
(a) Does its resistance increase, decrease, or stay the same? Explain,
(b) By what factor does its resistance change?
Solution:

Affiliate 21 Electric Current and Direct-Current Circuits Q.9CQ
What physical quantity do resistors connected in series have in mutual?
Solution:

Chapter 21 Electric Current and Direct-Current Circuits Q.9P

Solution:

Affiliate 21 Electrical Current and Direct-Current Circuits Q.10CQ
What concrete quantity do resistors continued in parallel take in mutual?
Solution:

Chapter 21 Electrical Electric current and Direct-Electric current Circuits Q.10P
Electric current-versus-voltage plots for two materials, A and B, are shown in Figure 21-26.
(a) Is the resistance of material A greater than, less than, or equal to the resistance of material B at the voltage V1?
(b) Choose the best caption from among the following:
I. Curve B is college in value than curve A.
Ii. A larger slope means a larger value of I/V, and hcnce a smaller value of R.
III. Curve B has the larger slope at the voltage V1 and hence the larger resistance.
Solution:

Chapter 21 Electric Electric current and Directly-Current Circuits Q.11CQ
Explain how electrical devices tin can begin operating almost immediately after yous throw a switch. fifty-fifty though private electrons in the wire may have hours to achieve the device
Solution:
Each electron in the wire affects its neighbors by ways of electric field exerting a force on them causing them to move
Thus when electrons begin to move out of a battery their move sets up a propagating influence that moves through the wire at nearly the speed of light causing electrons everywhere in the wire to brainstorm moving.
In this way electric device can begin operating about immediately afterwards nosotros throw a switch even though individual electrons in the wire may take hours to reach the device

Affiliate 21 Electric Current and Direct-Current Circuits Q.11P
2 cylindrical wires are made of the same material and accept the same length. If wire B is to have ix times the resistance of wire A, what must be the ratio of their radii, rB/rA?
Solution:

Chapter 21 Electrical Current and Direct-Current Circuits Q.12CQ
Explain the departure between resistivity and resistance.
Solution:

Chapter 21 Current and Direct-Electric current Circuits Q.12P
A silver wire is 5.ix 1000 long and 0.49 mm in diameter. What is its resistance?
Solution:

Chapter 21 Current and Straight-Current Circuits Q.13CQ
Explain why birds can roost on loftier-voltage wire without being electrocuted
Solution:
A number of factors come into play hera
—t Starting time the lesser of a bird'due south foot is tough and definitely not a skillful conductor of electricity.
—, Secondly the potential divergence is required for the flow of current thru the bird'southward body. contact with a high voltage wire isn't plenty to crusade a trouble. there need a contact with a lower voltage Source
But the bird is in contact with essentially the same loftier voltage in two unlike places (Where its ii feet touch the wire) which doesn't lead to a potential difference The only potential departure the bird feel is due to the very small voltage drop along the segment of wire between the bird's two feet

Affiliate 21 Electrical Current and Direct-Current Circuits Q.13P
When a potential difference of 18 5 is applied to a given wire, it conducts 0.35 A of electric current. What is the resistance of the wire?
Solution:

Chapter 21 Electrical Current and Direct-Current Circuits Q.14CQ
List two electric applications that would benefit from room-temperature superconductors. List two applications for which room-temperature superconductivity would not be beneficial.
Solution:
Magnetic resonance imaging (MRI) machines would definitely benefit from room temperature super conductivity
As information technology is. they must cool their magnets to police force temperature Similarly.
Electric ability transmission would do good if the resistance of the wires could exist eliminated On the other paw, a toaster or an electric oven requires resistance to practice its task: super electrical conductivity would not assist

Chapter 21 Current and Directly-Electric current Circuits Q.14P
The tungsten filament of a lightbulb has a resistance of 0.07 Ω. If the filament is 27 cm long, what is its diameter?
Solution:

Chapter 21 Electric Electric current and Direct-Electric current Circuits Q.15CQ
Oil what basic conservation laws are Kirchhoffs rules based?
Solution:
The junction rule is based on conservation of electrical charge the loop rule is based on the conservation energy

Chapter 21 Current and Directly-Current Circuits Q.15P
What is the resistance of six.0 mi of copper wire with a diameter of 0.55 mm?
Solution:

Chapter 21 Electric Current and Direct-Current Circuits Q.16CQ
What physical quantity do capacitors connected in series accept in common?
Solution:
Consider some capacitors connected in series with a battery The plate of the capacitor which is connected to the positive end of the bombardment volition learn positive charge and this will cause
same amount of negative accuse to develop at the other negative plate of the capacitor The negative charge will then cause the capacitor next to it to develop same amount of charge- In this fashion all the capacitors in the series connection volition get same amount of charga Hence, in a series connection, the concrete quantity that the capacitors have in common is the electric accuse

Chapter 21 Electric Current and Direct-Current Circuits Q.16P

Solution:

Chapter 21 Electrical Current and Direct-Current Circuits Q.17CQ
What concrete quantity do capacitors connected in parallel accept in mutual?
Solution:
When the capacitors are connected in parallel then the potential deviation is the common quantity on all the capacitors.

Chapter 21 Electrical Electric current and Directly-Current Circuits Q.17P
IP A bird lands on a blank copper wire carrying a electric current of 32 A. The wire is 8 gauge, which ways that its cantankerous-exclusive area is 0.thirteen cm2,
(a) Find the difference in potential between the bird'due south feet, bold they are separated past a altitude of 6.0 cm.
(b) Will your answer to office (a) increment or decrease if the separation between the bird's feet increases? Explain.
Solution:

Chapter 21 Electric Current and Direct-Current Circuits Q.18CQ

Solution:

Chapter 21 Electrical Current and Straight-Electric current Circuits Q.18P
A current of 0.96 A flows through a copper wire 0.44 mm in bore when it is connected to a potential difference of fifteen V. How long is the wire?
Solution:

Chapter 21 Electrical Current and Direct-Current Circuits Q.19P
IP BIO Current Through a Jail cell Membrane A typical jail cell membrane is 8.0 nm thick and has an electrical resistivity of ane.3 × 107 Ω · m.
(a) If the potential difference between the inner and outer surfaces of a cell membrane is 75 mV, how much electric current flows through a square area of membrane 1.0 μ m on a side?
(b) Suppose the thickness of the membrane is doubled,
simply the resistivity and potential difference remain the same. Does the current increase or decrease? By what factor?
Solution:

Chapter 21 Electric current and Straight-Electric current Circuits Q.20P
When a potential difference of 12 5 is applied to a wire half-dozen.9 thousand long and 0.33 mm in bore, the issue is an electrical electric current of 2.one A. What is the resistivity of the wire?
Solution:

Chapter 21 Electric Current and Direct-Current Circuits Q.21P
IP
(a) What is the resistance per meter of an aluminum wire with a cross-sectional area of 2.4 × 10-7 m2.
(b) Would your reply to function (a) increment, subtract, or stay the aforementioned if the bore of the wire were increased? Explain,
(c) Repeat part (a) for a wire with a cross-sectional area of 3.6 × 10−7 m2.
Solution:

Chapter 21 Electric Electric current and Direct-Electric current Circuits Q.22P
BIO Resistance and Current in the Human Finger The interior of the homo body has an electric resistivity of 0.fifteen Ω · m.
(a) Estimate the resistance for current flowing the length of your index finger. (For this calculation, ignore the much college resistivity of your skin.)
(b) Your muscles will contract when they comport a current greater than 15 mA. What voltage is required to produce this current through your finger?
Solution:

Chapter 21 Electrical Current and Direct-Current Circuits Q.23P
CE Lite A has iv times the power rating of light B when operated at the same voltage,
(a) Is the resistance of lite A greater than, less than, or equal to the resistance of light B? Explain,
(b) What is the ratio of the resistance of light A to the resistance of low-cal B?
Solution:

Chapter 21 Electric Current and Straight-Current Circuits Q.24P
CE Light A has iv times the power rating of low-cal B when operated at the aforementioned voltage.
(a) Is the resistance of calorie-free A greater than, less than, or equal to the resistance of light B? Explain.
(b) What is the ratio of the resistance of light A to the resistance of light B?
Solution:

Chapter 21 Current and Straight-Current Circuits Q.25P
CE Two lightbulbs operate on the same potential difference. Seedling Ahas iv times the power output of seedling B.
(a) Which seedling has the greater current passing through it? Explain,
(b) What is the ratio of the electric current in bulb A to the current in bulb B?
Solution:
Given that,
Ii lite bulbs operate on the same potential divergence. Seedling 'A' has four times the power output of bulb B.
(a) In terms of potential deviation 'V' and current 'I', the power output of the bulbs can exist written as
P = I V
It is given that 'V' is the aforementioned for both bulbs.
It follows, then, that the current in bulb 'A' is greater than the electric current in seedling 'B'
(b) Since power is proportional to current, the current in bulb 'A' is four times greater than the current in seedling B.

Chapter 21 Electric Electric current and Directly-Electric current Circuits Q.26P
CE Two lightbulbs operate on the same current. Bulb A has iv times the power output of seedling B.
(a) Is the potential difference across bulb A greater than or less than the potential departure across seedling B? Explain,
(b) What is the ratio of the potential difference across bulb A to that across bulb B?
Solution:
Given that,
Ii lite bulbs operate on the same electric current; Seedling 'A' has iv times the power output of bulb 'B'.
(a) In terms of potential difference 'V' and current 'I', the power output of the bulbs can exist written as
P = I 5
It is given that current 'I' is same for both bulbs.
It follows, that the potential difference in bulb 'A' is greater than the potential difference in seedling 'B'.
(b) Since power is proportional to potential difference, the potential difference in bulb 'A' is four times greater than the potential difference in bulb 'B'.
Chapter 21 Electric Current and Direct-Current Circuits Q.27P
A 75-5 generator supplies 3.8 kW of power. How much electric current does the generator produce?
Solution:

Chapter 21 Electric current and Direct-Electric current Circuits Q.28P
A portable CD player operates with a current of 22 mA at a potential deviation of 4.1 V. What is the power usage of the player?
Solution:

Chapter 21 Electric Current and Direct-Electric current Circuits Q.29P
Find the ability dissipated in a 25-Ω electric heater connected to a 120-V outlet.
Solution:

Chapter 21 Electric Electric current and Straight-Current Circuits Q.30P
The current in a 120-V reading lamp is ii.6 A. If the toll of electrical free energy is $0.075 per kilowatt-hour, how much does information technology cost to operate the light for
Solution:

Chapter 21 Current and Direct-Current Circuits Q.31P
It costs 2.6 cents to accuse a automobile battery at a voltage of 12 V and a electric current of 15 A for 120 minutes. What is the cost of electric energy per kilowatt-hour at this location?
Solution:

Chapter 21 Electric Current and Direct-Current Circuits Q.32P
IP A 75-W lightbulb operates on a potential difference of 95 Five. Notice
(a) the current in the bulb and
(b) the resistance of the bulb,
(c) If this bulb is replaced with i whose resistance is half the value found in part
(b), is its power rating greater than or less than 75 W? By what cistron?
Solution:

Affiliate 21 Electric Current and Direct-Current Circuits Q.33P
Rating Car Batteries Auto batteries are rated by the post-obit two numbers:
(ane) cranking amps = current the battery tin produce for xxx.0 seconds while maintaining a last voltage of at to the lowest degree vii.2 V and
(2) reserve capacity = number of minutes the bombardment can produce a 25-A electric current while maintaining a last voltage of at least 10.five V. I particular battery is advertised as having 905 cranking amps and a 155-minute reserve chapters. Which of these 2 ratings represents the greater corporeality of energy delivered by the battery?
Solution:

Chapter 21 Electric Current and Direct-Current Circuits Q.34P
CE Predict/Explain A dozen identical lightbulbs are connected to a given emf.
(a) Will the lights exist brighter if they are continued in series or in parallel?
(b) Choose the best caption from amidst the following:
I. When connected in parallel each bulb experiences the maximum emf and dissipates the maximum power.
II. Resistors in series accept a larger equivalent resistance and dissipate more power.
Three. Resistors in parallel have a smaller equivalent resistance and misemploy less power.
Solution:

Chapter 21 Electrical Current and Direct-Current Circuits Q.35P
CE Predict/Explain A fuse is a device to protect a circuit from the effects of a large current. The fuse is a small strip of metal that burns through when the current in it exceeds a certain value, thus producing an open circuit,
(a) Should a fuse be connected in serial or in parallel with the circuit it is intended to protect?
(b) Cull the best caption from amongst the following:
I. Either connection is acceptable; the main tiling is to accept a fuse in the excursion.
Ii. The fuse should be connected in parallel, otherwise it will interrupt the current in the circuit.
3. With the fuse connected in series, the current in the excursion drops to zero as soon as the fuse bruns through.
Solution:
(a) Fuse should be e'er connected in series.
If the fuse is connected in series, when the fuse is blown out it makes an open excursion and the appliances are protected from high current.
(b) If the fuse is connected in series and when the fuse is blown it becomes an open circuit and the electric current in the circuit becomes zero.
Hence best caption is III

Chapter 21 Electric Current and Direct-Current Circuits Q.36P
CE A circuit consists of iii resistors, R123, continued in series to a battery. Rank these resistors in club of increasing
(a) current through them and
(b) potential difference across them. Point ties where appropriate.
Solution:

Chapter 21 Electric Current and Straight-Current Circuits Q.37P
CE Predict/Explain 2 resistors are connected in parallel,
(a) If a third resistor is now connected in parallel with the original 2, does the equivalent resistance of the circuit increase, decrease, or remain the same?
(b) Choose the best explanation from amidst the following:
I. Adding a resistor generally tends to increase the resistance, but putting it in parallel tends to decrease the resistance; therefore the effects first and the resistance stays the same.
II. Calculation more resistance to the circuit will increment the equivalent resistance.
Iii. The third resistor gives yet another path for current to flow in the circuit, which means that the equivalent resistance is less.
Solution:

Chapter 21 Electric Electric current and Direct-Current Circuits Q.38P

Solution:
The equivalent resistance (R) of the resistors which are connected in series is equal to the sum of the resistance of the private resistors.

Chapter 21 Electric Current and Directly-Electric current Circuits Q.39P
What is the minimum number of 65-Ω resistors that must be connected in parallel to produce an equivalent resistance of 11 Ω or less?
Solution:

Chapter 21 Electric Current and Direct-Electric current Circuits Q.40P

Solution:

Chapter 21 Electric current and Direct-Electric current Circuits Q.41P
Your toaster has a power cord with a resistance of 0.020 Ω continued in series with a nine.vi-Ω nichrome heating element. If the potential deviation between the terminals of the toaster is 120 V, how much ability is dissipated in
(a) the power cord and
(b) the heating element?
Solution:

Chapter 21 Electrical Current and Direct-Current Circuits Q.42P
A hobbyist building a radio needs a 150-Ω resistor in her circuit, merely has only a 220-Ω, a 79-Ω, and a 92-Ω resistor available. How can she connect these resistors to produce the desired resistance?
Solution:

Chapter 21 Electric Current and Directly-Electric current Circuits Q.43P
A circuit consists of a 12.0-V battery connected to three resistors (42 Ω, 17 Ω, and 110 Ω) in series. Detect
(a) the current that flows through the battery and
(b) the potential deviation beyond each resistor.
Solution:

Chapter 21 Electric Current and Direct-Current Circuits Q.44P
IP Iii resistors, 11 Ω, 53 Ω, and R, are connected in series with a 24.0-5 battery. The full electric current flowing through the bombardment is 0.16 A.
(a) Find the value of resistance R.
(b) Find the potential difference across each resistor,
(c) If the voltage of the battery had been greater than 24.0 5, would your reply to part (a) have been larger or smaller? Explain.
Solution:

Affiliate 21 Electrical Current and Direct-Current Circuits Q.45P
A circuit consists of a battery connected to three resistors (65 Ω, 25 Ω, and 170 Ω) in parallel. The total current through the resistors is ane.8 A. Find
(a) the emf of the bombardment and
(b) the current through each resistor.
Solution:

Affiliate 21 Electric Current and Direct-Current Circuits Q.46P
IP Three resistors, 22 Ω, 67 Ω, and R, are continued in parallel with a 12.0-V battery. The total current flowing through the battery is 0.88 A.
(a) Discover the value of resistance R.
(b) Find the current through each resistor,
(c) If the total current in the battery had been greater than 0.88 A, would your respond to role (a) accept been larger or smaller? Explicate.
Solution:

Chapter 21 Electric Current and Direct-Current Circuits Q.47P
An 89-Ω resistor has a current of 0.72 A and is connected in series with a 130-Ω resistor. What is the emf of the battery to wliich the resistors are connected?
Solution:

Chapter 21 Electric Current and Directly-Current Circuits Q.48P

Solution:

Affiliate 21 Electric Electric current and Direct-Current Circuits Q.49P

Solution:

Chapter 21 Electric Electric current and Directly-Electric current Circuits Q.50P
How many 65-W lightbulbs tin be connected m parallel beyond a potential deviation of 85 5 before the full current in the circuit exceeds 2.1 A?
Solution:

Affiliate 21 Electrical Current and Direct-Current Circuits Q.51P

Solution:

Chapter 21 Electric Current and Direct-Electric current Circuits Q.52P
IP A 12-V bombardment is connected to terminals A and B in Figure 21-30.
(a) Given that R = 85 Ω, find the current in each resistor.
(b) Suppose the value of R is increased. For each resistor in plow, state whether the current flowing through it increases or decreases. Explain.
Solution:

Affiliate 21 Electric Current and Directly-Current Circuits Q.53P
IP The terminals A and B in Figure 21-31 are connected to a 9.0-V battery,
(a) Find the current flowing through each resistor,
(b) Is the potential divergence across the 6.iii-Ω resistor greater than, less than, or the same as the potential divergence across the i.5-Ω resistor? Explain.
Solution:

Chapter 21 Electric Electric current and Direct-Current Circuits Q.54P
IP Suppose the bombardment in Figure 21-32 has an internal resistance r = 0.25 Ω
(a) How much current flows through the bombardment?
(b) What is the potential difference betwixt the terminals of the bombardment? (c) If the 3.2-Ω resistor is increased in value, will the current in the battery increase or decrease? Explain.
Solution:

Chapter 21 Electric Electric current and Direct-Electric current Circuits Q.55P

Solution:

Chapter 21 Electric Current and Directly-Current Circuits Q.56P
The current in the thirteen.8-Ω resistor in Figure 21- 0.795 A. Observe the current in the other resistors in the circuit
Solution:

Affiliate 21 Electric current and Directly-Current Circuits Q.57P

Solution:

Chapter 21 Electric Current and Directly-Electric current Circuits Q.58P

Solution:

Chapter 21 Electrical Current and Direct-Current Circuits Q.59P
IP Suppose the polarity of the eleven.five-V battery in Figure 21-35 is reversed,
(a) Practise you expect this to increase or subtract the amount of current flowing in the excursion? Explain,
(b) Calculate the magnitude and management (clockwise or counterclockwise) of the current in this case.
Solution:

Chapter 21 Electrical Current and Direct-Current Circuits Q.60P
IP It is given that indicate A in Figure 21-35 is grounded (V = 0).
(a) Is the potential at point B greater than or less than zero? Explain,
(b) Is the potential at point C greater than or less than zero? Explain,
(c) Calculate the potential at bespeak D.
Solution:

Chapter 21 Electric Electric current and Direct-Current Circuits Q.61P

Solution:

Affiliate 21 Electrical Current and Straight-Current Circuits Q.62P
Suppose point A is grounded (Five = 0) in Figure 21-36. Observe the potential at points B and C.
Solution:

Chapter 21 Electrical Current and Direct-Current Circuits Q.63P

Solution:

Chapter 21 Current and Direct-Current Circuits Q.64P

Solution:

Affiliate 21 Electrical Electric current and Direct-Electric current Circuits Q.65P
CE Two capacitors, C1 = C and C2 = 2C, are connected to a battery,
(a) Which capacitor stores more than energy when they are connected to the bombardment in series? Explain,
(b) Which capacitor stores more than free energy when they are connected in parallel? Explain.
Solution:

Chapter 21 Electric Current and Straight-Current Circuits Q.66P
CE Predict/Explain Two capacitors are continued in series,
(a) If a third capacitor is now connected in series with the original two, does the equivalent capacitance increase, decrease, or remain the same?
(b) Choose the all-time explanation from among the following:
I. Calculation a capacitor generally tends to increase the capacitance, simply putting information technology in series tends to decrease the capacitance; therefore, the net result is no change.
Two. Adding a capacitor in series volition increase the total amount of charge stored, and hence increase the equivalent capacitance.
III. Calculation a capacitor in serial decreases the equivalent capacitance since each capacitor now has less voltage across it, and hence stores less charge.
Solution:

Chapter 21 Electric Current and Direct-Current Circuits Q.67P
CE Predict/Explain 2 capacitors are connected in parallel,
(a) If a third capacitor is at present connected in parallel with the original two, does the equivalent capacitance increment, decrease, or remain the aforementioned?
(b) Choose the best caption from among the following:
I. Calculation a capacitor tends to increase the capacitance, merely putting information technology in parallel tends to decrease the capacitance; therefore, the cyberspace result is no change.
II. Adding a capacitor in parallel will increment the total amount of charge stored, and hence increment the equivalent capacitance.
III. Adding a capacitor in parallel decreases the equivalent capacitance since each capacitor now has less voltage beyond it, and hence stores less accuse.
Solution:

Chapter 21 Electric Electric current and Directly-Current Circuits Q.68P

Solution:

Chapter 21 Electric Electric current and Direct-Electric current Circuits Q.69P
A 12-Five bombardment is continued to 3 capacitors in series. The capacitors have the following capacitances: four.v μ F, 12 μ F, and 32 μ F. Observe the voltage across the 32- μ F capacitor.
Solution:

Chapter 21 Electric Electric current and Direct-Current Circuits Q.70P
CE You acquit a series of experiments in which you connect the capacitors C1 and C2 > C1 to a battery in diverse ways. The experiments are as follows:
A, C1 lonely connected to the bombardment;
B, C2 alone connected to the bombardment;
C, C1 and C2 continued to the bombardment in serial;
D, C1 and C2 connected to the battery in parallel. Rank these iv experiments in order of increasing equivalent capacitance. Betoken ties where appropriate.
Solution:
The ranking is C<A<B<D
This follows because two capacitors in series have equivalent capacitances less than the smallest of the capacitor and two capacitor connected in parallel accept an equivalent capacitance greater than the largest of the capacitors.

Chapter 21 Electrical Current and Direct-Current Circuits Q.71P

Solution:

Affiliate 21 Electric Current and Directly-Electric current Circuits Q.72P
Terminals A and B in Effigy 21-39 are continued to a 9.0-Five battery. Find the energy stored in each capacitor.
Solution:
Therefore, energy stored incapacitor is approximately.

Affiliate 21 Electrical Electric current and Direct-Electric current Circuits Q.73P
IP Two capacitors, 1 7.5 μ F and the other 15 μ F, are connected in parallel across a fifteen-5 battery,
(a) Find the equivalent capacitance of the two capacitors,
(b) Which capacitor stores more charge? Explain,
(c) Find the charge stored on each capacitor.
Solution:

Affiliate 21 Electrical Current and Direct-Electric current Circuits Q.74P
IP Two capacitors, one vii.v μ F and the other 15 μ F, are connected in series across a xv-V bombardment,
(a) Find the equivalent capacitance of the two capacitors,
(b) Which capacitor stores more than charge? Explain,
(c) Observe the charge stored on each capacitor.
Solution:

Affiliate 21 Electric Current and Straight-Electric current Circuits Q.75P

Solution:

Affiliate 21 Electric Current and Direct-Current Circuits Q.76P
Two capacitors, C1 and C2, are connected in series and charged by a battery. Show that the energy stored in C1 plus the energy stored in C2 is equal to the energy stored in the equivalent capacitor, Ceq, when it is connected to the aforementioned battery.
Solution:

Chapter 21 Current and Direct-Current Circuits Q.77P

Solution:

Affiliate 21 Electric Electric current and Direct-Current Circuits Q.78P
The switch on an RC circuit is closed at t = 0. Given that ε = ix.0 V, R = 150 Ω, and C = 23 μ F, how much charge is on the capacitor at fourth dimension t = 4.2 ms?
Solution:

Chapter 21 Electric Electric current and Directly-Current Circuits Q.79P
ε The capacitor in an RC circuit (R = 120 Ω, C = 45 μ F) is initially uncharged. Find
(a) the charge on the capacitor and
(b) the current in the excursion in one case abiding (τ = RC) subsequently the circuit is connected to a 9.0-5 battery.
Solution:

Chapter 21 Electric Current and Direct-Current Circuits Q.80P

Solution:

Chapter 21 Electric Current and Straight-Current Circuits Q.81P
Consider an RC circuit with ε = 12.0 V, R = 175 Ω, and C = 55.seven μ F. Find
(a) the time constant for the circuit,
(b) the maximum charge on the capacitor, and
(c) the initial current in the excursion.
Solution:

Chapter 21 Electric Electric current and Directly-Current Circuits Q.82P
The resistor in an RC circuit has a resistance of 145 Ω.
(a) What capacitance must be used in this excursion if the time constant is to exist iii.5 ms?
(b) Using the capacitance determined in part (a), calculate the current in the circuit 7.0 ms later on the switch is closed. Assume that the capacitor is uncharged initially and that the emf of the battery is 9.0 V.
Solution:

Chapter 21 Electric Current and Directly-Electric current Circuits Q.83P
A flash unit of measurement for a camera has a capacitance of 1500 μ F. What resistance is needed in this RC circuit if the flash is to charge to 90% of its total charge in 21 due south?
Solution:

Chapter 21 Electric Current and Direct-Current Circuits Q.84P

Solution:

Affiliate 21 Electric Current and Direct-Current Circuits Q.85P

Solution:

Chapter 21 Current and Directly-Current Circuits Q.86P
The capacitor in an RC circuit is initially uncharged. In terms of R and C, determine
(a) the time required for the accuse on the capacitor to rise to 50% of its final value and
(b) the time required for the initial current to drib to ten% of its initial value.
Solution:

Chapter 21 Electric current and Directly-Electric current Circuits Q.87GP
CE A given automobile battery is rated equally 250 amp-hours. Is this rating a measure of energy, power, charge, voltage, or electric current? Explain.
Solution:

Chapter 21 Electrical Current and Directly-Current Circuits Q.88GP
CE Predict/Explain The resistivity of tungsten increases with temperature,
(a) When a light containing a tungsten filament heats upwards, does its ability consumption increment, decrease, or stay the same?
(b) Choose the best caption from amid the following:
I. The voltage is unchanged, and therefore an increase in resistance implies a reduced power, every bit we can run across from P = V2/R.
II. Increasing the resistance increases the power, as is clear from P = I2R.
Iii. The power consumption is independent of resistance, every bit we can see from P = IV.
Solution:

Affiliate 21 Electric current and Direct-Electric current Circuits Q.89GP
CE A cylindrical wire is to be doubled in length, but it is desired that its resistance remain the aforementioned,
(a) Must its radius be increased or decreased? Explain,
(b) By what factor must the radius exist changed?
Solution:

Chapter 21 Electric Current and Direct-Current Circuits Q.90GP
CE Predict/Explain An electric infinite heater has a power rating of 500 Due west when continued to a given voltage V.
(a) If two of these heaters are connected in series to the same voltage, is the power consiuned past the two heaters greater than, less than, or equal to 1000 West? (b) Choose the all-time caption from amongst the post-obit:
I. Each heater consumes 500 Due west; therefore ii of them will consume 500 W + 500 Due west = chiliad Westward.
II. The voltage is the aforementioned, but the resistance is doubled by connecting the heaters in scries. Therefore, the ability consumed (P = V2/R) is less than thousand West.
III. Connecting two heaters in serial doubles the resistance. Since power depends on the resistance squared, it follows that the power consumed is greater than 1000 W.
Solution:

Chapter 21 Electrical Current and Directly-Current Circuits Q.91GP
CE Two resistors, R1 = R and R2 = 2R, are connected to a bombardment.
(a) Which resistor dissipates more power when they are connected to the battery in series? Explain,
(b) Which resistor dissipates more power when they aie connected in parallel? Explicate.
Solution:

Chapter 21 Electric Electric current and Direct-Current Circuits Q.92GP

Solution:

Chapter 21 Electrical Current and Straight-Electric current Circuits Q.93GP
CE Predict/Explain
(a) Referring to Problem 92 arid the circuit in Figure 21-45, does the electric current supplied by the battery increase, decrease, or remain the aforementioned when the switch is closed?
(a) Choose the best explanation from among the following:
I. The current decreases considering just two resistors tin can depict current from the bombardment when the switch is closed.
II. Closing the switch makes no departure to the current since the second resistor is still connected to the bombardment as before.
Three. Closing the switch shorts out the second resistor, decreases the total resistance of the circuit, and increases the current.
Solution:

Chapter 21 Electrical Current and Direct-Current Circuits Q.94GP
CE Predict/Explain
(a) Referring to Trouble 92 and the circuit in Figure 21-45, does the total ability dissipated in the circuit increment, decrease, or remain the same when the switch is airtight?
(b) Choose the best explanation from amid the following:
I. Closing the switch shorts out 1 of the resistors, which ways that the power prodigal decreases.
Two. The equivalent resistance of the circuit is reduced past closing the switch, just the voltage remains the same. Therefore, from P = V2/R we see that the power prodigal increases.
III. The power dissipated remains the same because power, P = 4, is contained of resistance.
Solution:

Chapter 21 Electric current and Direct-Current Circuits Q.95GP

Solution:

Chapter 21 Electrical Current and Directly-Current Circuits Q.96GP
CE Predict/Explain
(a) When the switch is airtight in the circuit shown in Figure 21-46, does the current supplied by the battery increment, decrease, or stay the same?
(b) Choose the best caption from amongst the following:
I. The current increases because 3 resistors are drawing electric current from the battery when the switch is closed, rather than just ii.
II. Closing the switch makes no deviation to the current because the voltage is the aforementioned every bit before.
Three. Closing the switch decreases the electric current because an additional resistor is added to the circuit.
Solution:

Chapter 21 Current and Direct-Electric current Circuits Q.97GP
CE Predict/Explain
(a) When the switch is airtight in the excursion shown in Figure 21-46, does the full power prodigal in the excursion increase, decrease, or stay the same?
(b) Cull the best explanation from among the post-obit:
I. Closing the switch adds one more resistor to the excursion This makes it harder for the battery to supply current which decreases the power dissipated.
II. The equivalent resistance of the circuit is reduced by closing the switch, simply the voltage remains the same. Therefore from P = V2/R we see that the power dissipated increases
III. The power prodigal remains the same because power P = IV, is independent of resistance.
Solution:

Chapter 21 Electric Current and Direct-Current Circuits Q.98GP
Suppose that points A and B in Figure 21-30 are connected to a 12-Five battery. Find the ability prodigal in each of the resistors assuming that R = 65 Ω.
Solution:

Chapter 21 Electric Current and Direct-Current Circuits Q.99GP
You are given resistors of 413 Ω, 521 Ω, and 146 Ω. Describe how these resistors must be connected to produce an equivalent resistance of 255 Ω.
Solution:

Chapter 21 Electric Current and Direct-Current Circuits Q.100GP
You arc given capacitors of 18 μF, 7.two μF, and nine.0 μF. Describe how these capacitors must be connected to produce an equivalent capacitance of 22 μF.
Solution:

Chapter 21 Electric Current and Direct-Current Circuits Q.101GP
Suppose your car carries a chargc of 85 μC. What electric current does it produce as it travels from Dallas to Fort Worth (35 mi) in 0.75 h?
Solution:

Chapter 21 Current and Direct-Current Circuits Q.102GP

Solution:

Chapter 21 Electric Current and Direct-Electric current Circuits Q.103GP

Solution:

Affiliate 21 Electric Current and Direct-Current Circuits Q.104GP
Information technology is desired to construct a 5.0-Ω resistor from a ane.2-m length of tungsten wire. What bore is needed for this wire?
Solution:

Chapter 21 Electric Current and Direct-Electric current Circuits Q.105GP
Electrical Safety Codes For condom reasons, electrical codes accept been established that limit the amount of current a wire of a given size can carry. For example, an 18-estimate (cross- sectional area = 1.17 mm2), rubber-insulated extension cord with copper wires tin can comport a maximum current of 5.0 A. Notice the voltage drop in a 12-ft, xviii-gauge extension cord carrying a electric current of five.0 A. (Note: In an extension cord, the current must flow through two lengths—down and back.)
Solution:

Chapter 21 Electrical Current and Straight-Current Circuits Q.106GP

Solution:

Chapter 21 Current and Straight-Electric current Circuits Q.107GP
A portable CD player uses a current of 7.5 mA at a potential difference of 3.5 5.
(a) How much energy does the role player use in 35 s?
(b) Suppose the player has a mass of 0.65 kg. For what length of time could the player operate on the free energy required to lift it through a height of i.0 m?
Solution:

Affiliate 21 Electric Current and Straight-Current Circuits Q.108GP
An electrical heating gyre is immersed in 4.6 kg of water at 22 °C. The coil, which has a resistance of 250 Ω, warms the water to 32 °C in 15 min. What is the potential difference at
which the roll operates?
Solution:

Chapter 21 Electric Current and Direct-Current Circuits Q.109GP

Solution:

Chapter 21 Electrical Current and Direct-Current Circuits Q.110GP
A silver wire and a copper wire have the same volume and the same resistance. Find the ratio of their radii, r argent/r copper·
Solution:

Chapter 21 Electric current and Direct-Current Circuits Q.111GP
2 resistors are continued in series to a battery with an emf of 12 V. The voltage across the offset resistor is 2.7 V and the current through the second resistor is 0.15 A. Find the resistance of the two resistors.
Solution:

Chapter 21 Electric Current and Direct-Electric current Circuits Q.112GP
BIOPacemaker Pulses A pacemaker sends a pulse to a patient'southward heart every time the capacitor in the pacemaker charges to a voltage of 0.25 V. It is desired that the patient receive 75 pulses per minute. Given that the capacitance of the pacemaker is 110 μF and that the battery has a voltage of 9.0 V, what value should the resistance have?
Solution:

Chapter 21 Electric Current and Direct-Current Circuits Q.113GP
A long, thin wire has a resistance R. The wire is now cutting into iii segments of equal length, which are connected in parallel. In terms of R, what is the equivalent resistance of the three wire segments?
Solution:

Chapter 21 Electric Current and Straight-Current Circuits Q.114GP

Solution:

Chapter 21 Electric current and Directly-Current Circuits Q.115GP
IP Suppose we connect a 12.0-V battery to terminals A and B in Figure 21-29.
(a) Is the current in the 45-Ω resistor greater than, less than, or the same as the current in the 35-Ω resistor? Explain,
(b) Summate the current flowing through each of the 3 resistors in this excursion.
Solution:

Affiliate 21 Electric Current and Straight-Current Circuits Q.116GP
IP Suppose the bombardment in Figure 21-50 has an internal resistance of 0.73 Ω.
(a) What is the potential departure across the terminals of the bombardment when the switch is open up?
(b) When the switch is closed, does the potential divergence of the battery increase or decrease? Explain,
(c) Find the potential difference across the battery after the switch has been airtight a long time.
Solution:

Affiliate 21 Electric current and Direct-Current Circuits Q.117GP

Solution:

Chapter 21 Electric Current and Direct-Current Circuits Q.118GP
IP 15.0-V bombardment is connected to terminals A and B in Figure 21-41.
(a) Given that C = xv.0 μF, notice the charge on each of the capacitors,
(b) Find the full energy stored in this system,
(c) If the 7.22-μF capacitor is increased in value, will the total free energy stored in the circuit increase or decrease? Explicate.
Solution:

Chapter 21 Electric Current and Directly-Electric current Circuits Q.119GP
IP The switch in the RC circuit shown in Figure 21-44 is airtight at t = 0.
(a) How much power is dissipated in each resistor just after t = 0 and in the limit t → ∞?
(b) What is the charge on the capacitor at the time t = 0.35 ms?
(c) How much energy is stored in the capacitor in the limit t → ∞??
(d) If the voltage of the battery is doubled, by what factor does your answer to office (c) modify? Explain.
Solution:

Affiliate 21 Electric Current and Direct-Current Circuits Q.120GP
Ii resistors, R1 and R2, are connected in parallel and connected to a battery. Show that the power prodigal in R1 plus the power dissipated in R2 is equal to the power dissipated in the equivalent resistor, Req, when it is connected to the aforementioned battery.
Solution:

Chapter 21 Electric Current and Direct-Current Circuits Q.121GP
A battery has an emf ε and an internal resistance r. When the bombardment is connected to a 25-Ω resistor, the current through the battery is 0.65 A. When the battery is connected to a 55-Ω resistor, the current is 0.45 A. Find the bombardment's emf and internal resistance.
Solution:
Calculate battery's emf and internal resistance by applying Kirchhoff's loop rule to the circuit.
Kirchhoff'south loop rule states that as one moves around a closed loop in a circuit, the algebraic sum of the potential difference must be zero.

Chapter 21 Electric Current and Direct-Current Circuits Q.122GP
When two resistors, R1 and R2, are connected in series across a 6.0-Five battery, the potential deviation across R1 is 4.0 V. When R1 and R2 are connccted in parallel to the aforementioned battery, the current through R2 is 0.45 A. Find the values of R1 and R2.
Solution:

Chapter 21 Electric Current and Directly-Current Circuits Q.123GP
Suppose the voltmeter measures a potential departure of 3.70 Five beyond the resistor. What is the current that flows through the person's body?
A. three.70 × 10-6A
B. 5.00 × 10-5A
C. 0.0740 A
D. 3.70 A
Solution:

Chapter 21 Electric Current and Direct-Electric current Circuits Q.124PP
What is the resistance of the person and footwear when the voltmeter reads 3.70 V?
A. one.25 × 107Ω
B. 1.35 × 107 Ω
C. iv.63 × 107 Ω
D. 1.71 × 108 Ω
Solution:

Chapter 21 Electric Electric current and Direct-Current Circuits Q.125PP
The resistance of a given person and footwear is 4.00 × 107Ω What is the reading on the voltmeter when this person is tested?
A. 0.976 V
B. 1.22 Five
C. 1.25 V
D. 50.0 V
Solution:

Chapter 21 Electric Current and Direct-Current Circuits Q.126PP
The resistance of a given person and footwear is 4.00 × 107Ω What is the reading on the voltmeter when this person is tested?
A. 0.976 5
B. 1.22 V
C. 1.25 Five
D. 50.0 V
Solution:

Affiliate 21 Electric current and Direct-Current Circuits Q.127PP
Suppose that during one test a person'southward shoes become wet when water spills onto the floor. When this happens, practice you expect the reading on the voltmeter to increase, subtract, or stay the same?
Solution:
Given if the shoes become wet the resistance of the person pes wear will be decreased and the current menstruation will be increased. This results increase in the voltmeter reading.

Chapter 21 Electric Current and Direct-Current Circuits Q.128IP
Referring to Case 21-7 Suppose the iii resistors in this circuit have the values R1 = 100.0 Ω, R2 = 200.0 Ω, and R3 = 300.0 Ω, and that the emf of the battery is 12.0 5. (The resistor numbers are given in the Interactive Figure.)
(a) Notice the potential difference across each resistor,
(b) Notice the current that flows through each resistor.
Solution:

Chapter 21 Electric Current and Straight-Current Circuits Q.129IP
Referring to Example 21-7 Suppose R1 = R2 = 225 Ω and R3 = R. The emf of the bombardment is 12.0 V. (The resistor numbers are given in the Interactive Effigy.)
(a) Find the value of R such that the electric current supplied by the battery is 0.0750 A. (b) Find the value of R that gives a potential difference of two.65 V across resistor 2.
Solution:

Affiliate 21 Electric Current and Direct-Current Circuits Q.130IP
IP Referring to Case 21-9 Suppose the resistance of the 126-Ω resistor is reduced by a factor of 2. The other resistor is 275 Ω, the capacitor is 182 μF, and the battery has an emf of iii.00 Five.
(a) Does the filial value of the charge on the capacitor increase, decrease, or stay the same? Explicate,
(b) Does the time for the capacitor to charge to lxxx.0% of its last value increase, subtract, or stay the same? Explain, (c) Detect the fourth dimension referred to in role (b).
Solution:

Affiliate 21 Electrical Current and Direct-Current Circuits Q.131IP
IP Referring to Example 21-9 Suppose the capacitance of the 182-μF capacitor is reduced past a gene of ii. The two resistors are 126 Ω and 275 Ω, and the battery has an emf of 3.00 V.
(a) Discover the terminal value of the charge on the capacitor,
(b) Does the time for the capacitor to charge to fourscore.0% of its final value increase, decrease, or stay the aforementioned? Explicate,
(c) Find the time referred to in part (b).
Solution:

mccordcouleas.blogspot.com

Source: https://www.aplustopper.com/mastering-physics-solutions-chapter-21-electric-current-and-direct-current-circuits/

Share this post