Q: A battery has a potential difference of $$V_{ab} = 1.5$$ volts between its terminals, as shown in the image. What is the energy gained by an electron (charge $$e = 1.6 \times 10$$^{-19}$$ C) when it moves from point b$ to point a$?

$$-2.4 \times 10$$^{-19}$$ J ($$since the electron moves from lower to higher potential, $$\Delta U = q\Delta V$)

Question 1

A battery has a potential difference of $$V_{ab} = 1.5$$ volts between its terminals, as shown in the image. What is the energy gained by an electron (charge $$e = 1.6 	imes 10$$^{-19}$$ C) when it moves from point b$ to point a$?

Accepted Answer

$$-2.4 	imes 10$$^{-19}$$ J ($$since the electron moves from lower to higher potential, $$\Delta U = q\Delta V$)

Question 2

Which of the following statements about electric potential is correct?

Accepted Answer

Electric potential is the potential energy per unit charge.

Question 3

For a positive point charge, as shown in the second image, how does the electric potential $$V$$ change as you move outward from the charge?

Accepted Answer

$$V$$ decreases as you move outward.

Question 4

The potential difference $$\Delta V$$ between two points $$A$$ and $$B in a $$uniform electric field $$E$$ separated by distance $$d is $$given by:

Accepted Answer

$$\Delta V = -Ed$$

Question 5

Which of the following best describes an equipotential surface?

Accepted Answer

A surface where the electric potential is the same at every point.

Question 6

What is the angle between an electric field line and an equipotential surface where they intersect?

Accepted Answer

90°

Question 7

A proton is released from rest in a uniform electric field. As it moves, what happens to its electric potential energy and kinetic energy?

Accepted Answer

Potential energy decreases, kinetic energy increases.

Question 8

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

Accepted Answer

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

Question 9

If two point charges $$q_1$$ and $$q_2$$ are separated by a distance $$r_{12}$$, what is the potential energy $$U of $$the system?

Accepted Answer

$$U = \frac{q_1$ q_2$}{4\pi\$$epsilon_0$$ r_{12}}$$

Question 10

A rod of length $$l$$ with total charge $$Q is $$placed along the $$x-$$axis. What is the expression for the electric potential $$V at a $$point $$P on $$the $$y-$$axis a distance $$d$$ from the origin?

Accepted Answer

$$V = \frac{Q}{4\pi\$$epsilon_0$$ l} \ln \left( \frac{l + \sqrt{l^2$ + d^2$}}{d} \right)$$

Question 11

Which of the following is true about the superposition principle for electric potential?

Accepted Answer

The total electric potential is the scalar sum of the potentials from each charge.

Question 12

A charge $$q$$ moves through a potential difference $$\Delta V. $$The work done by the electric field is:

Accepted Answer

$$W = q\Delta V$$

Question 13

Which of the following is the correct unit equivalence for the electric field $$E$$?

Accepted Answer

$$1\ \mathrm{N/C} = 1\ \mathrm{V/m}$$

Question 14

A system consists of three point charges $$q_1$$, $$q_2$$, and $$q_3 at $$distances $$r_{12}$$, $$r_{13}$$, and $$r_{23}$$ from each other. The total potential energy $$U of $$the system is:

Accepted Answer

$$U = \frac{q_1$ q_2$}{4\pi\$$epsilon_0$$ r_{12}} + \frac{q_1$ q_3$}{4\pi\$$epsilon_0$$ r_{13}} + \frac{q_2$ q_3$}{4\pi\$$epsilon_0$$ r_{23}}$$

Question 15

The electron volt (eV) is defined as:

Accepted Answer

The energy required to move an electron through a potential difference of 1 V.

Question 16

If the electric field $$\vec{E} is $$known, the potential difference between points $$A$$ and $$B$$ can be found using:

Accepted Answer

$$\Delta V = -\int_A^B \vec{E} \cdot d\vec{s}$$

Question 17

Which of the following statements about the reference point for electric potential is correct?

Accepted Answer

The reference point for electric potential can be chosen arbitrarily, commonly at infinity or ground.

Question 18

Which of the following best describes the relationship between electric field lines and equipotential surfaces?

Accepted Answer

Electric field lines are always perpendicular to equipotential surfaces.

Question 19

A charge $$q is $$moved from point $$A to $$point $$B in an $$electric field. The change in potential energy $$\Delta U is $$given by:

Accepted Answer

$$\Delta U = q(V_B - V_A)$$

Week 3 Lec. 2

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