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.
answer
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. Explanation: A) This statement is true. When an electric field is applied to a conductor, the free electrons in the conductor will experience a force in the direction opposite the applied electric field. This force will cause the free electrons to move in the direction opposite the applied electric field.B) This statement is true. By convention, the direction of a current is taken to be the direction of flow for negative charges. This convention is used because electrons are the charge carriers in most conductors, and electrons have a negative charge.C) This statement is true. In order to maintain a steady flow of current in a conductor, a steady force must be maintained on the mobile charges. This force is provided by the electric field that is created by the voltage difference between the two terminals of the circuit.D) This statement is true. Current is the total amount of charge that passes through a conductor's full cross section at any point per unit of time.E) This statement is false. In a circuit, current is delivered by the positive terminal of a battery, but it is not used up by the time it returns to the negative terminal of the battery. The current flows through the circuit and returns to the battery, where it is used up.
question
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.
answer
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.
question
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.
answer
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.
question
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.
answer
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. Explanation: The resistivity of a material is a measure of how strongly it resists the flow of electric current. The resistance of a material is a measure of how strongly it opposes the flow of electric current. The resistivity of a material is inversely proportional to the conductivity of the material. The resistance of a material is directly proportional to the resistivity of the material. The resistance of a material is directly proportional to the length of the material. The resistance of a material is inversely proportional to the cross-sectional area of the material.Given that the two wires have the same cross-sectional area, we can say that wire A has twice the resistance of wire B. This is because the resistance of a material is directly proportional to the length of the material.
question
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.
answer
C)The current is doubled. Explanation: If the voltage across a circuit of constant resistance is doubled, the current in the circuit is also doubled. This is because the voltage is directly proportional to the current in a circuit with constant resistance.
question
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.
answer
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 Explanation: If the resistance in a circuit connected to a constant current is halved, the voltage in the circuit is doubled. This is because the voltage across a circuit is directly proportional to the current passing through it. In other words, the voltage is proportional to the resistance. Therefore, if the resistance is halved, the voltage is doubled.
question
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.
answer
B)The power dissipated is reduced by a factor of 2. Explanation: If the resistance of the element is doubled, the power dissipated by this element will be reduced by a factor of 2.
question
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.
answer
D)The power dissipated is quadrupled. Explanation: The power dissipated by the circuit is doubled when the current is doubled. This is because the power dissipated is equal to the current squared multiplied by the resistance. Therefore, when the current is doubled, the power dissipated is also doubled.
question
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.
answer
D)The resistance increases as temperature increases. Explanation: The resistance of most metals increases as the temperature of the metal increases. The reason for this is that the atoms in the metal vibrate more at higher temperatures, making it more difficult for the electrons to flow freely through the metal.
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