Deck 22: Current and Resistance

Question 1

When a voltage difference is applied to a piece of copper wire,a 5.0 mA current flows.If the copper wire is replaced with a silver wire with twice the diameter of the copper wire,how much current will flow through the silver wire? The lengths of both wires are the same,and the voltage difference remains unchanged.(The resistivity of copper is 1.68 × 10^-8 Ω·m,and the resistivity of silver is 1.59 × 10^-8 Ω·m. )

A)21 mA
B)19 mA
C)11 mA
D)5.3 mA

Answer 1

21 mA

Question 2

A battery is rated that it provides 1.0 mW of power at 9.0 V when fully charged.How much current can it deliver?

A)0.11 mA
B)81 kA
C)0.33 mA
D)9.0 kA

Answer 2

0.11 mA

Question 3

A 3.0 V battery that can store 400.0 J of energy is connected to a resistor.How much electrical charge must flow between the battery's terminals to completely drain the battery if it is fully charged?

A)130 C
B)0.01 C
C)1200 C
D)0.02 C

Answer 3

130 C

Question 4

A rechargeable battery that is completely drained of electrical energy can be completely charged by applying 6.0 mA of current for 1.0 h.If the battery acquires an emf of 1.0 V in the process of being charged,how much energy is the battery capable of storing?

A)22 J
B)6.0 mJ
C)0.20 kJ
D)1.7 μJ

Question 5

The resistivity of gold is 2.44 × 10^-8 Ω·m at a temperature of 20°C.A gold wire,0.5 mm in diameter and 44 cm long,carries a current of 380 ma.The number of electrons per second passing a given cross section of the wire is closest to:

A)2.4 × 10¹⁸
B)2.4 × 10¹⁷
C)1.2 × 10²²
D)2.8 × 10¹⁴
E)6.3 × 10¹⁵

Question 6

A jeweler needs to electroplate gold (atomic mass 196.97 u)onto a bracelet.He knows that the charge carriers in the ionic solution are gold ions,and has calculated that he must deposit 0.20 g of gold to reach the necessary thickness.How much current does he need to plate the bracelet in 3.0 hours? (Avogadro's number is 6.02 × 10²³. )

A)9.1 mA
B)540 mA
C)33 A
D)1800 mA

Question 7

How much current will be flowing through a 40.0 m length of copper wire with radius 4.0 mm if it is connected to a source supplying 16.0 V? (The resistivity of copper is 1.68 × 10^-8 Ω·m. )

A)1200 A
B)9.5 x 10⁸ A
C)68 nA
D)710 A

Question 8

As current flows through a uniform wire,the wire gets hotter because the electrons slow down and therefore transform their lost kinetic energy into thermal energy in the wire.

Question 9

A wire has a current of 6.0 mA in it.How many electrons pass a given point in a minute?

A)2.3 × 10¹⁸
B)360
C)6.3 × 10¹⁴
D)5.4 × 10^-15

Question 10

In the metal wires of a circuit,the electron current i flows from the negative to the positive end of a battery,but the current I flows from the positive to the negative end of the battery.

Question 11

When current is flowing in a metal,the electrons are moving at nearly the speed of light.

Question 12

A tube of mercury with resistivity 9.84 × 10^-7 Ω·m has a 23.0 N/C electric field inside the column of mercury.How much current is flowing,if the diameter of the tube is ?

A)18 A
B)180 A
C)29 A
D)280 A

Question 13

A 4.0 m length of gold wire is connected to a 1.5 V battery,and a current of 4.0 mA flows through it.What is the diameter of the wire? (The resistivity of gold is 2.44 × 10^-8 Ω·m. )

A)17 μm
B)8.5 μm
C)48 μm
D)9.0 μm

Question 14

A device experiences a voltage drop of 4.0 V across it while a current of 4.0 mA flows through it.How much power does it dissipate?

A)16 mW
B)64 μW
C)4.0 kW
D)1.0 kW

Question 15

A 5.0 V battery storing 43.0 kJ of energy supplies 1.5 A of current to a circuit.How much energy does the battery have left after powering the circuit for 1.0 h?

A)16 kJ
B)27 kJ
C)43 kJ
D)41 kJ

Question 16

The heater element of a 120 V toaster is a 5.4 m length of nichrome wire,whose diameter is 0.48 mm.The resistivity of nichrome at the operating temperature of the toaster is 1.3 × 10^-6 Ω·m.The toaster is operated at a voltage of 120 V.The power drawn by the toaster is closest to:

A)370 W
B)360 W
C)380 W
D)400 W
E)410 W

Question 17

A battery does 10.0 J of work moving 4.0 C of charge between its terminals.What is the emf of the battery?

A)2.5 V
B)0.63 V
C)40 V
D)160 V

Question 18

The resistivity of gold is 2.44 × 10^-8 Ω·m at a temperature of 20°C.A gold wire,1.8 mm in diameter and 14 cm long,carries a current of 480 ma.The power dissipated in the wire is closest to:

A)0.31 mW
B)0.077 mW
C)0.14 mW
D)0.19 mW
E)0.25 mW

Question 19

A component with a 17 Ω resistor is rated for use at power levels not exceeding 14 W.How much current can safely flow through the component?

A)0.91 A
B)1.21 A
C)238 A
D)0.22 A

Question 20

A device with a resistance of 200.0 kΩ is connected to a 9.0 V battery.How much power does the device use?

A)0.41 mW
B)16,000 kW
C)0.045 mW
D)1800 kW

Question 21

Lightening is a discharge of electrons that commonly is greater than is needed to neutralize a positive charge.A series of strokes,each in the opposite direction of the previous stroke,occur to overcome this excessive discharge.Why do all of these strokes follow the same path,causing a flickering effect?

Question 22

Why is it that electrons rather than positive ions flow from a wire?

Question 23

The charge carriers in metals are electrons,but this is not necessarily true for other types of material.

Question 24

A copper wire of length L and radius b is attached to another copper wire of length L and radius 2b,forming one long wire of length 2L.This long wire is attached to a battery,and a current is flowing through it.Relative to the electric field within the wire of radius b,the magnitude of the electric field within the wire of radius 2b is

A)four times weaker.
B)four times stronger.
C)two times weaker.
D)two times stronger.
E)equal.

Question 25

If there is an electric field inside of a conductor,then current must be flowing through this conductor.

Question 26

The direction of the current I in a metal wire is the same as the direction of the internal electric field in the wire but it is opposite to the direction the electrons are moving.

Question 27

If you double the diameter of a cylindrical wire,you double its conductivity but reduce its resistivity by one half.

Question 28

Which has the higher resistance,a piece of wire with diameter d or a piece of wire the same length,composed of the same material,but having a diameter

Question 29

If the length and diameter of a wire of circular cross section are both doubled,the resistance is

A)unchanged.
B)doubled.
C)increased fourfold.
D)halved.
E)None of these are true.

Question 30

If a one-amp current is flowing in a wire,one electron per second flows through this wire.

Question 31

Where does the energy go that an electron has gained from the electric field when the electron passes through a conductor that has resistivity?

Question 32

Copper wire #1 has a length L and a radius b.Copper wire #2 has a length 2L and a radius 2b.Which statement is true?

A)The total resistance of wire #1 is twice as high as that of wire #2.
B)The total resistance of wire #1 is equal to that of wire #2.
C)The total resistance of wire #1 is half that of wire #2.
D)The total resistance of wire #1 is four times higher than that of wire #2.

Question 33

A current flowing through a copper wire (which is connected to a battery)is due to

A)electrons being accelerated by an electric field.
B)positively charged particles being pushed off the battery terminal.
C)electrons being bumped by positively charged particles.
D)positively charged particles being attracted to the negative terminal of a battery.