Question 1

Which of the following statements about equipotential surfaces is correct?

Accepted Answer

The electric field is always perpendicular to equipotential surfaces.

Question 2

A point charge $$q$$ creates an electric potential $$V at a $$distance $$r. $$Which equation correctly gives the potential at that point?

Accepted Answer

$$V = \dfrac{kq}{r}$$

Question 3

A parallel-plate capacitor is connected to a battery and then the battery is disconnected. If the plates are pulled farther apart, what happens to the voltage across the plates?

Accepted Answer

The voltage increases.

Question 4

Which of the following correctly expresses the energy stored in a capacitor?

Accepted Answer

$$U = \dfrac{CV^2$}{2}$$

Question 5

A wire of length $$L$$ and cross-sectional area $$A is $$made of a material with resistivity $$\rho. $$What is the resistance $$R of $$the wire?

Accepted Answer

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

Question 6

Which of the following is true for resistors connected in series?

Accepted Answer

The same current flows through each resistor.

Question 7

A battery with emf $$\mathcal{E}$$ and internal resistance $$r is $$connected to an external resistor $$R. $$What is the current in the circuit?

Accepted Answer

$$I = \dfrac{\mathcal{E}}{R + r}$$

Question 8

Which equation gives the power dissipated in a resistor $$R$$ carrying current $$I$$?

Accepted Answer

$$P = I^2$ R$$

Question 9

A system consists of three point charges: $$q_1$$, $$q_2$$, and $$q_3. $$What is the total electric potential energy $$U of $$the system?

Accepted Answer

$$U = k\left(\dfrac{q_1$ q_2$}{r_{12}} + \dfrac{q_1$ q_3$}{r_{13}} + \dfrac{q_2$ q_3$}{r_{23}}\right)$$

Question 10

Which of the following is true for capacitors connected in parallel?

Accepted Answer

The total capacitance is the sum of the individual capacitances.

Question 11

A cylindrical capacitor consists of two coaxial cylinders of length $$L$$, inner radius $$a$$, and outer radius $$b. $$What is its capacitance?

Accepted Answer

$$C = 2\pi \$$varepsilon_0$$ \dfrac{L}{\ln(b/a)}$$

Question 12

Which of the following best describes the direction of motion for a negative charge in an electric field?

Accepted Answer

It moves toward regions of higher electric potential.

Question 13

A current $$I$$ flows through a wire with cross-sectional area $$A. If $$the current density is $$J$$, which equation is correct?

Accepted Answer

$$I = J A$$

Question 14

Which of the following is a correct statement about conductors in electrostatic equilibrium?

Accepted Answer

The electric field inside the conductor is zero.

Question 15

A battery of emf $$\mathcal{E}$$ and negligible internal resistance is connected to three resistors $$R_1$$, $$R_2$$, and $$R_3 in $$parallel. What is the total current supplied by the battery?

Accepted Answer

$$I = \mathcal{E}\left(\dfrac{1}{R_1$} + \dfrac{1}{R_2$} + \dfrac{1}{R_3$}\right)$$

Question 16

A spherical capacitor consists of two concentric spheres of radii $$a$$ and $$b$$ ($$b \u003e a). $$What is the capacitance?

Accepted Answer

$$C = 4\pi \$$varepsilon_0$$ \dfrac{ab}{b-a}$$

Question 17

Which of the following is the correct expression for the electric field in terms of the electric potential $$V$$?

Accepted Answer

$$\vec{E} = -
abla V$$

Question 18

A dipole with dipole moment $$p is $$placed at a point on the axis at a distance $$r$$ from its center. What is the electric potential at that point?

Accepted Answer

$$V = \dfrac{p \cos 	heta}{4\pi \$$varepsilon_0$$ r^2$}$$

Question 19

A resistor of $$10\ \Omega is $$connected to a $$20\ V$$ battery. How much power is dissipated in the resistor?

Accepted Answer

$$P = \dfrac{V^2$}{R} = \dfrac{20^2$}{10} = 40\ W$$

Physics II: Electric Potential, Capacitance, Current, Resistance, and Circuits – Midterm 2 Study Guide

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