Exam 25: Current,resistance,and Electromotive Force

A wire has a cross-sectional area of 0.10 mm².If there are 4.0 × 10²⁸ atoms per cubic meter in this wire,and if each atom contributes 2 free electrons,what is the drift velocity of the electrons when the current in the wire is 6.0 A? (e = 1.60 × 10^-19 C)

Building codes usually limit the current carried by a No.14 copper wire to 15 A.Many household circuits are wired with this size wire.What is the drift velocity of the electrons in this case? The diameter of this wire is 1.6 mm.Assume one conduction electron per atom in copper.The atomic weight of copper is 63.3 g/mol and its density is 8900 kg/m³.Avogadro's number is 6.022 × 10²³ molecules/mol and .

A cylindrical wire of radius 2.0 mm carries a current of 2.5 A.The potential difference between points on the wire that are 46 m apart is 3.7 V. (a)What is the electric field in the wire? (b)What is the resistivity of the material of which the wire is made?

You are given a copper bar of dimensions 3 cm × 5 cm × 8 cm and asked to attach leads to it in order to make a resistor. (a)If you want to achieve the SMALLEST possible resistance,you should attach the leads to the opposite faces that measure A)3 cm × 5 cm. B)3 cm × 8 cm. C)5 cm × 8 cm. D)Any pair of faces produces the same resistance. (b)If you want to achieve the LARGEST possible resistance,you should attach the leads to the opposite faces that measure A)3 cm × 5 cm. B)3 cm × 8 cm. C)5 cm × 8 cm. D)Any pair of faces produces the same resistance.

The resistivity of gold is 2.44 × 10^-8 Ω • m at room temperature.A gold wire that is 1.8 mm in diameter and 11 cm long carries a current of 170 mA.How much power is dissipated in the wire?

A narrow copper wire of length L and radius b is attached to a wide 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.If the electric field in the narrow wire is E,the electric field in the wide wire is

A 400-W computer (including the monitor)is turned on for 8.0 hours per day.If electricity costs 10¢ per kWh,how much does it cost to run the computer annually for a typical 365-day year?

In the figure,when the terminal voltage V_ab of the battery is equal to 20 V,how much current passes through the battery,including its direction?

The heater element of a particular 120-V toaster is a 8.9-m length of nichrome wire,whose diameter is 0.86 mm.The resistivity of nichrome at the operating temperature of the toaster is 1.3 × 10^-6 Ω • m.If the toaster is operated at a voltage of 120 V,how much power does it draw?

In the figure a current of 6.0 A is drawn from the battery.What is the terminal voltage V_ab of the battery?

Calculate the current through a 10.0-m long 22 gauge (having radius 0.321 mm)nichrome wire if it is connected to a 12.0-V battery.The resistivity of nichrome is 100 × 10^-8 Ω • m.

A silver wire has a cross sectional area A = 2.0 mm².A total of 9.4 × 10¹⁸ electrons pass through the wire in 3.0 s.The conduction electron density in silver is 5.8 × 10²⁸ electrons/m³ and .What is the drift velocity of these electrons?

If the current density in a wire or radius R is given by J = kr,0 < r < R,what is the current in the wire?

When a voltage difference is applied to a piece of metal wire,a current flows through it.If this metal wire is now replaced with a silver wire having twice the diameter of the original 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 the original metal is 1.68 × 10^-8 Ω • m,and the resistivity of silver is 1.59 × 10^-8 Ω • m.)

The power rating of a 400-Ω resistor is 0.800 W. (a)What is the maximum voltage that can be applied across this resistor without damaging it? (b)What is the maximum current this resistor can draw without damaging it?

If a current of 2.4 A is flowing in a cylindrical wire of diameter 2.0 mm,what is the average current density in this wire?

Nichrome wire,often used for heating elements,has resistivity of 1.0 × 10^-6 Ω • m at room temperature.What length of No.30 wire (of diameter 0.250 mm)is needed to wind a resistor that has 50 ohms at room temperature?

A certain electric furnace consumes 24 kW when it is connected to a 240-V line.What is the resistance of the furnace?

What length of a certain metal wire of diameter 0.15 mm is needed for the wire to have a resistance of 15 Ω? The resistivity of this metal is 1.68 × 10^-8 Ω • m.

The current in a wire varies with time according to the equation ,where t is in seconds.How many coulombs of charge pass a cross section of the wire in the time period between and