Question 1

A battery is connected to a light bulb as shown in the image. Which of the following statements best describes the direction of the electric current in the wires connecting the battery to the bulb?

Accepted Answer

The current flows from the positive terminal of the battery to the negative terminal through the wires.

Question 2

Consider a parallel-plate capacitor with plate area $$A$$ and separation $$d$$, charged to a potential difference $$V_{ab}. $$What is the expression for its capacitance in vacuum?

Accepted Answer

$$C = \$$varepsilon_0$$ \frac{A}{d}$$

Question 3

In a conductor without an internal electric field, how do electrons move?

Accepted Answer

They move randomly with no net displacement.

Question 4

A cylindrical conductor contains positive charge carriers. If the electric field $$\vec{E}$$ points to the right, what is the direction of the current $$I$$?

Accepted Answer

To the right, same as $$\vec{E}.$$

Question 5

A cylindrical conductor contains negative charge carriers (electrons). If the electric field $$\vec{E}$$ points to the right, what is the direction of the current $$I$$?

Accepted Answer

To the right, same as $$\vec{E}.$$

Question 6

Which of the following best describes the drift velocity of electrons in a conductor with an applied electric field?

Accepted Answer

Electrons move randomly but have a small net velocity opposite to the electric field.

Question 7

The resistance $$R of a $$wire of length $$L$$ and cross-sectional area $$A$$ made of material with resistivity $$\rho is $$given by:

Accepted Answer

$$R = \frac{\rho L}{A}$$

Question 8

Which of the following statements about the temperature dependence of resistivity in metals is correct?

Accepted Answer

Resistivity increases as temperature increases.

Question 9

A parallel-plate capacitor is charged and then disconnected from the battery. If the plate separation is increased, which of the following quantities increases?

Accepted Answer

Voltage across the plates

Question 10

A parallel-plate capacitor is connected to a battery. If a dielectric material with dielectric constant $$K \u003e 1 is $$inserted between the plates, what happens to the charge stored on the capacitor?

Accepted Answer

It increases.

Question 11

Which of the following is the correct expression for the energy stored in a capacitor with capacitance $$C$$ and voltage $$V$$?

Accepted Answer

$$U = \frac{1}{2}CV^2$

Question 12

Two identical capacitors are connected in parallel to a battery of voltage $$V. $$What is the equivalent capacitance?

Accepted Answer

$$C_{eq} = 2C$$

Question 13

Two identical capacitors are connected in series to a battery of voltage $$V. $$What is the equivalent capacitance?

Accepted Answer

$$C_{eq} = \frac{C}{2}$$

Question 14

A wire of length $$L$$ and cross-sectional area $$A is $$made of a material with resistivity $$\rho. If $$the length is doubled and the area is halved, what happens to the resistance?

Accepted Answer

It becomes four times larger.

Question 15

Which of the following best describes the effect of inserting a dielectric with dielectric constant $$K$$ between the plates of a capacitor, while keeping the charge constant?

Accepted Answer

The voltage decreases by a factor of $$K.$$

Question 16

The current density $$J in a $$conductor is related to the electric field $$E by$$:

Accepted Answer

$$J = \sigma E$$

Question 17

Which of the following materials would have the lowest resistivity at room temperature?

Accepted Answer

Copper

Question 18

A cylindrical resistor is made of a material with resistivity $$\rho$$, length $$L$$, and cross-sectional area $$A. If $$the temperature increases, what happens to the resistance if the material is a metal?

Accepted Answer

Resistance increases.

Question 19

Which of the following is true about the direction of current and electric field in a conductor with positive charge carriers?

Accepted Answer

Current flows in the same direction as the electric field.

Question 20

Which of the following is the correct formula for the temperature dependence of resistivity in a metal?

Accepted Answer

$$\rho(T) = \$$rho_0$$[1 + \alpha(T - T_0$)]$$

Electric Current, Resistance, and Capacitance: Study Notes for Physics with Calculus

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