Question 1

Which of the following statements about electric potential energy $$U_e is $$correct?

Accepted Answer

It depends only on the location of the charges, not on the path used for assembly.

Question 2

A proton and an electron are brought closer together from an initial separation $$r_i to a $$final separation $$r_f$$ ($$r_f \u003c r_i). $$What happens to the electric potential energy of the system?

Accepted Answer

It decreases because opposite charges attract.

Question 3

For two point charges $$q_1$$ and $$q_2$$ separated by a distance $$r$$, what is the formula for their electric potential energy?

Accepted Answer

$$U_e = \frac{kq_1q_2}{r}$$

Question 4

If both $$q_1$$ and $$q_2$$ are positive, what must be done to bring them closer together?

Accepted Answer

Work must be done by an external agent against the electric field.

Question 5

What is the electric potential $$V at a $$distance $$r$$ from a point charge $$Q$$?

Accepted Answer

$$V = \frac{kQ}{r}$$

Question 6

A charge $$q$$ moves through a potential difference $$\Delta V. $$What is the change in its potential energy?

Accepted Answer

$$\Delta U_e = q \Delta V$$

Question 7

An electron is accelerated from rest through a potential difference $$\Delta V$$ and reaches a speed $$v_f. $$Which equation relates $$\Delta V to$$ $$v_f$$?

Accepted Answer

$$\Delta V = \frac{mv_f^2$}{2q}$$

Question 8

Given a uniform electric field $$E$$ along the $$y-$$direction, what is the potential difference between $$y=0$$ and $$y=a$$?

Accepted Answer

$$V = -Ea$$

Question 9

Which of the following is true about equipotential surfaces?

Accepted Answer

The electric field is perpendicular to equipotential surfaces.

Question 10

What is the electric potential at a point due to a system of $$n$$ point charges $$Q_i$$ located at distances $$r_i$$ from the point?

Accepted Answer

$$V = \frac{1}{4\pi\$$epsilon_0$$} \sum_{i=1}^n \frac{Q_i}{r_i}$$

Question 11

How is the electric field $$\vec{E}$$ related to the electric potential $$V$$?

Accepted Answer

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

Question 12

Which property is true for an isolated conductor in electrostatic equilibrium?

Accepted Answer

The electric field inside the conductor is zero.

Question 13

What is the electric flux $$\Phi_E$$ through a closed surface enclosing a net charge $$Q$$?

Accepted Answer

$$\Phi_E = \frac{Q}{\$$epsilon_0$$}$$

Question 14

Which Gaussian surface would you choose to calculate the electric field at a distance $$r$$ from a long, straight, uniformly charged rod?

Accepted Answer

A cylindrical surface of radius $$r$$ and length $$L.$$

Question 15

Why does Gauss's Law simplify the calculation of the electric field for an infinite line of charge but not for a finite line?

Accepted Answer

Because the field lines are radial and symmetric only for an infinite line.

Question 16

A conducting spherical shell has a charge $$+q$$ placed at its center and no excess charge on the conductor. What is the charge per unit area induced on the inner surface?

Accepted Answer

It is $$-q$$ divided by the inner surface area.

Question 17

If the electric field inside a conductor is zero, what can be said about the electric potential inside the conductor?

Accepted Answer

It is constant throughout the conductor.

Question 18

A charge $$+2e$$ moves from a point at $$500.0 kV to a $$point at $$200.0 kV. $$What is the change in its kinetic energy?

Accepted Answer

$$+600$$ keV

Question 19

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

Accepted Answer

It is an equipotential surface.

Electric Potential and Gauss’ Law – Study Notes

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