Exam 17: Current and Resistance

Ten coulombs of charge start from the negative terminal of a battery, flow through the battery and then leave the positive terminal through a wire, flow through a resistor and then return to the starting point on this closed circuit.In this complete process, the ten coulombs:

If a light bulb has half the resistance of a 100-W lightbulb, what would be its wattage? Assume both bulbs are attached to the same 120-V circuit.

A superconducting wire's chief characteristic is which of the following?

A certain material is in a room at 27 $\degree$ C.If the absolute temperature (K) of the material is tripled, its resistance doubles.(Water freezes at 273 K.) What is the value for a, the temperature coefficient of resistivity?

The heating coil of a hot water heater has a resistance of 20 W and operates at 210 V.How long a time is required to raise the temperature of 200 kg of water from 15 $\degree$ C to 80 $\degree$ C? (The specific heat for water = 10³ cal/kg* $\degree$ C and 1.0 cal = 4.186 J).

A 60-W light bulb is in a socket supplied with 120 V.What is the current in the bulb?

In a certain material there is a current of 16 A flowing through a surface to the right, and there is an equal amount of positive and negative charge passing through the surface producing the current.How much negative charge passes through the surface?

Which is not a force?

Replacing a wire resistor with another of the same material and length but with three times the diameter will have the effect of changing the resistance by what factor?

The unit of electric resistance, the ohm, is equivalent to which of the following?

By what factor is the resistance of a copper wire changed when its temperature is increased from 20 $\degree$ C to 120 $\degree$ C? The temperature coefficient of resistivity for copper = 3.9 * 10^-3 ( $\degree$ C)^-1.

A flashlight bulb operating at a voltage of 4.5 V has a resistance of 8.0 W.How many electrons pass through the bulb filament per second (e = 1.6 * 10^-19 C)?

A 0.20-m-long metal rod has a radius of 1.0 cm and a resistance of 3.2 * 10^-5 W.What is the resistivity of the metal?

A tungsten wire is used to determine the melting point of indium.The resistance of the tungsten wire is 3.000 W at 20 $\degree$ C and increases to 4.850 W as the indium starts to melt.a_tungsten = 4.50 * 10^-3 ( $\degree$ C)^-1.What is the melting temperature of indium?

If a 500-W heater carries a current of 4.00 A, what is the resistance of the heating element?

Carbon has a negative temperature coefficient of resistance of -0.5 * 10^-3 ( $\degree$ C)^-1.What temperature increase would result in a resistance decrease of 1% for a carbon resistor?

If a certain resistor obeys Ohm's law, its resistance will change:

The number density of conduction electrons in a metal can be found from the density r of the metal, the mass per mole M of the metal, the number of conduction electrons per metal atom, and Avogadro's number N_A.If we assume one conduction electron per atom, which of the following gives the number density of conduction electrons for a given metal?

An electric toaster requires 1 100 W at 110 V.What is the resistance of the heating coil?

A Nichrome wire has a radius of 0.50 mm and a resistivity of 1.5 * 10^-6 W*m.What is the resistance per unit length of this wire?