Q: An electron is accelerated from rest through a potential difference of $$5000\ \mathrm{V}. $$What is the change in its potential energy?

$$-8 \times 10$$^{-16}$$\ \mathrm{J}$$

Question 1

A book is lifted from the floor to a shelf, increasing its gravitational potential energy. Which of the following best describes the relationship between the work done by your hand and the change in the book's gravitational potential energy $$\Delta U_g$$?

Accepted Answer

The work done by your hand is equal to the increase in gravitational potential energy.

Question 2

A spring is compressed by a force $$\vec{F}$$, storing elastic potential energy $$U_s. $$Which equation correctly relates the work done $$W to $$the change in elastic potential energy $$\Delta U_s$$?

Accepted Answer

$$\Delta U_s = W$$

Question 3

A positive charge $$q is $$pushed toward a group of stationary positive charges. What happens to the electric potential energy $$U_{elec} of $$the system?

Accepted Answer

It increases because work is done against the electric force.

Question 4

Which of the following correctly expresses the work done by the electric force when moving a charge from point $$a to $$point $$b$$?

Accepted Answer

$$W = U_b - U_a$$

Question 5

A parallel plate capacitor has a potential difference $$V_{ba} = 50\ \mathrm{V}$$ and plate separation $$d = 5.0\ \mathrm{cm}. $$What is the magnitude of the electric field $$E$$ between the plates?

Accepted Answer

$$E = 1000\ \mathrm{V/m}$$

Question 6

For a point charge $$Q$$, the electric potential at a distance $$r is $$given by which of the following expressions?

Accepted Answer

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

Question 7

A negative charge is placed near the negative plate of a parallel plate capacitor. If released, which way will it move and what happens to its electric potential energy?

Accepted Answer

It moves toward the positive plate and its potential energy decreases.

Question 8

Which of the following statements about equipotential surfaces is correct?

Accepted Answer

Equipotential surfaces are always perpendicular to electric field lines.

Question 9

A $$1\ \mu\mathrm{C}$$ charge is moved from point $$A to $$point $$B in an $$electric field, and $$3.0\ \mu\mathrm{J} of $$work is done. What is the potential difference $$V_B - V_A$$?

Accepted Answer

$$3000\ \mathrm{V}$$

Question 10

Which of the following is true about the potential energy of a system of two point charges $$q_1$$ and $$q_2$$ separated by a distance $$r$$?

Accepted Answer

$$U = k\frac{q_1$ q_2$}{r}$$

Question 11

An electron is accelerated from rest through a potential difference of $$5000\ \mathrm{V}. $$What is the change in its potential energy?

Accepted Answer

$$-8 	imes 10$$^{-16}$$\ \mathrm{J}$$

Question 12

Which of the following best describes why the electric potential is considered a scalar quantity?

Accepted Answer

Because it only has magnitude and can be added algebraically.

Question 13

A $$2\ \mu\mathrm{C}$$ charge is brought from infinity to a point $$0.1\ \mathrm{m}$$ from a $$5\ \mu\mathrm{C}$$ charge. What is the electric potential energy of the system? ($$k = 9 	imes 10^9$\ \mathrm{N\cdot m^2$/C^2$$}$)

Accepted Answer

$$0.45\ \mathrm{J}$$

Question 14

Which of the following is true about the work required to move a charge along an equipotential surface?

Accepted Answer

The work is zero.

Question 15

A $$1\ \mathrm{C}$$ charge is moved from a point at $$2\ \mathrm{V} to a $$point at $$0\ \mathrm{V}. $$What is the work done by the electric force?

Accepted Answer

$$-2\ \mathrm{J}$$

Question 16

Which of the following is the correct relationship between electric field $$E$$ and electric potential $$V in a $$region of constant field?

Accepted Answer

$$E = -\frac{\Delta V}{d}$$

Question 17

A system consists of three charges: $$q_1 = +1$$\ \mu\mathrm{C}$$, q_2$ = -1\ \mu\mathrm{C}$$, $$q_3 = +2$$\ \mu\mathrm{C}$$, each separated by 2$$\ \mathrm{cm}$$. What is the total energy required to assemble this system from infinity?

Accepted Answer

$$-0.45\ \mathrm{J}$$

Question 18

Which of the following is the correct definition of the electron volt (eV)?

Accepted Answer

The energy gained by an electron moving through a potential difference of $$1\ \mathrm{V}.$$

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