Q: A charge moves $$1.9 m at$$ $$45^\circ to a $$uniform electric field of $$7.0 N/C. $$What is the potential difference $$\Delta V$$ experienced by the charge?

$$\Delta V = -(E)(1.9\,\text{m})\cos(45^\circ)$$

Question 1

Which equation gives the electric potential $$V at a $$distance $$r$$ from a single point charge $$q in $$vacuum?

Accepted Answer

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

Question 2

A collection of point charges $$q_i$$ are located at distances $$r_i$$ from a point. What is the total electric potential $$V at $$that point?

Accepted Answer

$$V = \frac{1}{4\pi\$$epsilon_0$$} \sum_i \frac{q_i}{r_i}$$

Question 3

Which of the following best describes an equipotential surface in an electric field?

Accepted Answer

A surface on which all points have the same electric potential.

Question 4

If a positive charge moves from a region of higher potential to a region of lower potential, what happens to its electric potential energy?

Accepted Answer

It decreases.

Question 5

An electron ($$m = 9.11 	imes 10$$^{-31}$$ kg, q = -1.6$$ 	imes $$10^{-19} C) is $$accelerated through a potential difference of $$5000 V in a TV $$picture tube. What is its final speed?

Accepted Answer

$$v = \sqrt{\frac{2q\Delta V}{m}}$$

Question 6

Which of the following correctly relates the electric field $$\vec{E} to $$the electric potential $$V in $$one dimension?

Accepted Answer

$$E = -\frac{dV}{dx}$$

Question 7

A charge moves $$1.9 m at$$ $$45^\circ to a $$uniform electric field of $$7.0 N/C. $$What is the potential difference $$\Delta V$$ experienced by the charge?

Accepted Answer

$$\Delta V = -(E)(1.9\,	ext{m})\cos(45^\circ)$$

Question 8

Which statement about equipotential surfaces and electric field lines is correct?

Accepted Answer

Equipotential surfaces are always perpendicular to electric field lines.

Question 9

A topographic map analogy is used to describe electrostatics. What do valleys/depressions represent?

Accepted Answer

Regions of negative electric potential.

Question 10

What is the work $$W$$ required to move a charge $$q$$ through a potential difference $$\Delta V$$?

Accepted Answer

$$W = q\Delta V$$

Question 11

A negative charge will naturally move from a region of ______ potential to a region of ______ potential to reduce its potential energy.

Accepted Answer

lower; higher

Question 12

Given a continuous distribution of charge, what is the expression for the electric potential $$V at a $$point?

Accepted Answer

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

Question 13

If the electric field points to the right, which surface is at a higher potential: surface A (left) or surface B (right)?

Accepted Answer

Surface A

Question 14

Which of the following is true about the change in electric potential energy $$\Delta U$$ when a charge $$q$$ moves through a potential difference $$\Delta V$$?

Accepted Answer

$$\Delta U = q\Delta V$$

Question 15

Which mathematical operation relates the electric field $$\vec{E} to $$the electric potential $$V in $$three dimensions?

Accepted Answer

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

Question 16

A positive test charge is placed at a point in an electric field. The electric potential at that point is determined by:

Accepted Answer

The work needed to bring a unit positive charge from infinity to that point.

Question 17

Which of the following is the correct expression for the potential difference $$\Delta V$$ between two points separated by distance $$d in a $$uniform electric field $$E$$?

Accepted Answer

$$\Delta V = -E d$$

Question 18

In the context of electrostatics, what does the 'steepness' of equipotential lines on a topographic map analogy represent?

Accepted Answer

The magnitude of the electric field.

Question 19

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

Accepted Answer

$$U = \frac{1}{4\pi\$$epsilon_0$$} \frac{q_1$ q_2$}{r}$$

Electric Potential & Equipotential Surfaces (PHYS 133: Physics II, Ch. 23: 3-4)

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