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Exam 22: Current and Resistance

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Question 21

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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

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Question 22

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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

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Question 23

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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.

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:

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

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 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?

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

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

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. )

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

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