Question 1

A metal bucket with a metal lid has zero excess charge. You place a metal ball with an excess of positive charge, $$+q$$, inside the bucket, but the ball does not touch the bucket. At electrostatic equilibrium, what is the excess charge on the inner and outer surfaces of the bucket?

Accepted Answer

The inner surface has charge $$-q$$ and the outer surface has charge $$+q.$$

Question 2

A parallel-plate capacitor is fully charged by a battery and then disconnected. If the separation between the plates is doubled, what happens to the electric field between the plates?

Accepted Answer

The electric field remains the same.

Question 3

The electric potential energy stored in a system of two point charges $$q_1$$ and $$q_2$$ separated by a distance $$r is $$given by which equation?

Accepted Answer

$$U_{elec} = \frac{K q_1$ q_2$}{r}$$

Question 4

A parallel-plate capacitor is fully charged by a battery and then disconnected. If the area of the plates is halved, what happens to the potential difference between the plates?

Accepted Answer

The potential difference doubles.

Question 5

A proton is fixed at the origin. A second particle with charge $$q_2$$ \u003c 0$$ is a distance d$ away and moving away from the proton with kinetic energy K_2$. Under which condition is the second particle bound to the proton?

Accepted Answer

$$K_2$$ \u003c \frac{K e $$q_2$$}{d}$$

Question 6

The electric potential at a distance $$r$$ from a point charge $$q is $$given by:

Accepted Answer

$$V = \frac{1}{4\pi\$$epsilon_0$$} \frac{q}{r}$$

Question 7

A parallel-plate capacitor is fully charged by a battery and then disconnected. A dielectric is inserted between the plates. What happens to the potential difference between the plates?

Accepted Answer

It decreases.

Question 8

Which of the following changes will increase the current through a wire by a factor of 4, assuming the potential difference is constant?

Accepted Answer

Increase the radius of the wire by a factor of 2.

Question 9

The energy stored in a capacitor is given by which of the following equations?

Accepted Answer

$$U_C = \frac{Q^2$}{2C}$$

Question 10

A parallel-plate capacitor is fully charged by a battery and then disconnected. The plates are pulled apart until the separation doubles. What is the ratio of the final to initial electrostatic energies, $$\frac{U_f}{U_i}$$?

Accepted Answer

$$2$$

Question 11

The electric field in a region is described by $$E = -\frac{dV}{dx}. If $$the potential $$V$$ decreases linearly with $$x$$, what is the nature of the electric field?

Accepted Answer

The electric field is constant and points in the direction of increasing $$x.$$

Question 12

Two metal spheres, A and B, are connected by a long conducting wire. Sphere A has twice the radius of sphere B. After electrostatic equilibrium is reached, which of the following is true?

Accepted Answer

The potential at the surface of A equals that at B.

Question 13

A parallel-plate capacitor is fully charged by a battery and then disconnected. If the area of the plates is halved, what happens to the electric field between the plates?

Accepted Answer

The electric field doubles.

Question 14

Which of the following best describes the function of an electrostatic precipitator in a coal-burning power plant?

Accepted Answer

It uses a strong electric field to remove smoke particles from waste gas.

Question 15

The current density $$J in a $$wire is related to the electric field $$E$$ and the conductivity $$\sigma by $$which equation?

Accepted Answer

$$J = \sigma E$$

Question 16

A vertical wire carries current upward through the center of a horizontal table. A compass rests on the table. In which direction does the north pole of the compass point?

Accepted Answer

Tangential to the circle centered on the wire, following the right-hand rule.

Question 17

Which of the following statements about the electric potential at a point $$P a $$distance $$r$$ from a charge $$Q_S$$ are correct? Assume the potential is zero at infinity.

Accepted Answer

If $$Q_S is $$negative, $$V_P \u003c 0.$$

Question 18

A parallel-plate capacitor is fully charged by a battery. The positive plate has charge $$+q$$ and the negative plate has charge $$-q. $$What happens to the charge on the plates when the separation between plates is doubled while the battery is still connected?

Accepted Answer

The charge halves.

Question 19

The energy density (energy per unit volume) of the electric field in a capacitor is given by:

Accepted Answer

$$u_E = \frac{1}{2} \$$epsilon_0$$ E^2$

Electrostatics, Electric Potential, and Capacitance: Study Notes with Applications

스터디 가이드 - 연습 문제

학습 가이드 - 플래시카드