Chapter 25

Which of the following statements are true? Pick all that apply. A)Good conductors of electricity have larger conductivity values than insulators. B)The resistance of a conductor is proportional to the resistivity of the material of which the conductor is composed. C)A material that obeys Ohm's law reasonably well is called an ohmic conductor or a linear conductor. D)Semiconductors have resistivity values that are larger than those of insulators. E)The resistance of a conductor is proportional to the conductivity of the material of which the conductor is composed.

A)Good conductors of electricity have larger conductivity values than insulators. B)The resistance of a conductor is proportional to the resistivity of the material of which the conductor is composed. C)A material that obeys Ohm's law reasonably well is called an ohmic conductor or a linear conductor.

Which of the following will increase the resistance of a wire? Pick all that apply. A)Increasing the length of the wire will increase the resistance of the wire. B)Increasing the resistivity of the material the wire is composed of will increase the resistance of the wire. C)Decreasing the length of the wire will increase the resistance of the wire. D)Decreasing the cross-sectional area of the wire will increase the resistance of the wire. E)Increasing the cross-sectional area of the wire will increase the resistance of the wire. F)Decreasing the resistivity of the material the wire is composed of will increase the resistance of the wire.

A)Increasing the length of the wire will increase the resistance of the wire. B)Increasing the resistivity of the material the wire is composed of will increase the resistance of the wire. D)Decreasing the cross-sectional area of the wire will increase the resistance of the wire.

A constant voltage is applied across a circuit element. If the resistance of the element is doubled, what is the effect on the power dissipated by this element? A)The power dissipated is reduced by a factor of 4. B)The power dissipated is reduced by a factor of 2. C)The power dissipated is doubled. D)The power dissipated remains constant. E)The power dissipated is quadrupled.

B)The power dissipated is reduced by a factor of 2.

If the resistance in a circuit connected to a constant current is halved, how is the voltage in the circuit affected? A)The voltage is doubled. B)The voltage is reduced by a factor of 2. C)The voltage is reduced by a factor of 4. D)The voltage remains constant. E)The voltage is quadrupled.

B)The voltage is reduced by a factor of 2. ohms law V=IR if halfed V=(IR)/2 then V/2 = IR thus reduced by 2

Consider two copper wires with the same cross-sectional area. Wire A is twice as long as wire B. How do the resistivities and resistances of the two wires compare? Pick all that apply. A)Wire A and wire B have the same resistance. B)Wire A has twice the resistance of wire B. C)Wire A and wire B have the same resistivity. D)Wire A has twice the resistivity of wire B. E)Wire B has twice the resistivity of wire A. F)Wire B has twice the resistance of wire A.

B)Wire A has twice the resistance of wire B. C)Wire A and wire B have the same resistivity. Because it is longer the resistance is twice. Because they are the same material they have the same resistivity.

Which of the following statements are true? Pick all that apply. A)When an electric field is applied to a conductor, the free electrons move only in the direction opposite the applied electric field. B)By convention, the direction of a current is taken to be the direction of flow for negative charges. C)In order to maintain a steady flow of current in a conductor, a steady force must be maintained on the mobile charges. D)Current is the total amount of charge that passes through a conductor's full cross section at any point per unit of time. E)In a circuit, current is delivered by the positive terminal of a battery, and it is used up by the time it returns to the negative terminal of the battery.

C)In order to maintain a steady flow of current in a conductor, a steady force must be maintained on the mobile charges. D)Current is the total amount of charge that passes through a conductor's full cross section at any point per unit of time.

If the voltage across a circuit of constant resistance is doubled, how is the current in the circuit affected? A)The current is reduced by a factor of 2. B)The current remains constant. C)The current is doubled. D)The current is quadrupled. E)The current is reduced by a factor of 4.

C)The current is doubled.

A circuit maintains a constant resistance. If the current in the circuit is doubled, what is the effect on the power dissipated by the circuit? A)The power dissipated remains constant. B)The power dissipated is doubled. C)The power dissipated is reduced by a factor of 2. D)The power dissipated is quadrupled. E)The power dissipated is reduced by a factor of 4.

D)The power dissipated is quadrupled.

What happens to the resistance of most common metals as the temperature of the metal increases? A)The resistance remains constant as temperature increases. B)The resistance decreases as temperature increases. C)Whether resistance increases or decreases as temperature increases depends on the type of metal. D)The resistance increases as temperature increases.

D)The resistance increases as temperature increases.