Q: A proton is fixed at the origin. An electron orbits the proton at a radius of $$0.053 nm. $$What is the electric field at the position of the electron due to the proton? ($$k = 9.0 \times 10^9$\ \mathrm{N\cdot m^2$/C^2$$}$$, e = 1.60$$ \times $$10^{-19}$ C)

$$5.1 \times 10$$^{11}$$\ \mathrm{N/C}$$

Q: A small bead with charge $$+10 nC is at $$the origin. What is the magnitude of the electric field at the point $$(3.0\ \mathrm{cm}, 4.0\ \mathrm{cm})$$?

$$6.0 \times 10^4$\ \mathrm{N/C}$$

Q: Which of the following is the correct value for the permittivity of free space $$\$$epsilon_0$$?

$$8.85 \times 10$$^{-12}$$\ \mathrm{C^2$/(N\cdot m^2$)}$$

Question 1

Which of the following correctly describes the direction of the electric field produced by a point charge $$q$$?

Accepted Answer

The electric field points away from $$q if$$ $$q \u003e 0$$ and toward $$q if$$ $$q \u003c 0.$$

Question 2

What is the magnitude of the electric field at a distance $$r$$ from a point charge $$q in $$vacuum?

Accepted Answer

$$E = \frac{k|q|}{r^2$}$$

Question 3

A proton is fixed at the origin. An electron orbits the proton at a radius of $$0.053 nm. $$What is the electric field at the position of the electron due to the proton? ($$k = 9.0 	imes 10^9$\ \mathrm{N\cdot m^2$/C^2$$}$$, e = 1.60$$ 	imes $$10^{-19}$ C)

Accepted Answer

$$5.1 	imes 10$$^{11}$$\ \mathrm{N/C}$$

Question 4

A small bead with charge $$+10 nC is at $$the origin. What is the magnitude of the electric field at the point $$(3.0\ \mathrm{cm}, 4.0\ \mathrm{cm})$$?

Accepted Answer

$$6.0 	imes 10^4$\ \mathrm{N/C}$$

Question 5

Which principle allows you to calculate the net electric field from multiple point charges?

Accepted Answer

Superposition principle

Question 6

Two charges, $$Q_1 = +7.00$$\ \mu\mathrm{C}$$ and Q_2$ = -5.00\ \mu\mathrm{C}$$, are placed at $$(0,0)$$ and $$(0.3, 0)$$ meters, respectively. What is the direction of the electric field at point $$P$$ located at $$(0.4, 0)$$ meters?

Accepted Answer

Toward $$Q_2 (to $$the left)

Question 7

Which of the following statements about the electric field inside a parallel-plate capacitor is correct?

Accepted Answer

The electric field is uniform in both magnitude and direction.

Question 8

What is the formula for the electric field between two parallel plates with charge $$\pm Q$$, area $$A$$, and separation $$d$$?

Accepted Answer

$$E = \frac{Q}{\$$epsilon_0$$ A}$$

Question 9

Which of the following is NOT a property of electric field lines?

Accepted Answer

Field lines can cross each other.

Question 10

A droplet of oil with mass $$m = 0.01 g $$and charge $$q = -2.0\ \muC is $$suspended in air. What electric field is required to balance the droplet's weight? ($$g = 9.8\ \mathrm{m/s^2$})$$

Accepted Answer

$$E = \frac{mg}{|q|}$$

Question 11

An electron enters a uniform electric field $$E = 5000\ \mathrm{N/C}$$ with an initial horizontal velocity $$v_{0x} = 5.0 	imes 10^6$\ \mathrm{m/s}. $$What is the acceleration of the electron due to the field? ($$e = 1.6 	imes 10$$^{-19}$$ C, m_e = 9.11$$ 	imes $$10^{-31} kg)$$

Accepted Answer

$$a = \frac{eE}{m_e}$$

Question 12

Which of the following best describes the electric field lines for a dipole?

Accepted Answer

They start on the positive charge and end on the negative charge, curving outward between the charges.

Question 13

If the charge density on the plates of a parallel-plate capacitor is increased, what happens to the electric field between the plates?

Accepted Answer

The electric field increases.

Question 14

A point charge $$+Q is $$placed at the center of a conducting spherical shell with charge $$-Q. $$What is the direction of the electric field inside the shell but outside the point charge?

Accepted Answer

Zero everywhere

Question 15

Which of the following is true about the electric field at the center of a square with three charges $$+Q$$, $$+Q$$, and $$-Q at $$three corners?

Accepted Answer

The direction depends on the vector sum of the fields from each charge.

Question 16

A charged particle moves in a uniform electric field between two parallel plates. Which of the following best describes its trajectory?

Accepted Answer

It follows a parabolic path.

Question 17

Which of the following is the correct value for the permittivity of free space $$\$$epsilon_0$$?

Accepted Answer

$$8.85 	imes 10$$^{-12}$$\ \mathrm{C^2$/(N\cdot m^2$)}$$

Question 18

Which of the following best explains why the shape of the electrodes in a parallel-plate capacitor does not affect the uniformity of the electric field (as long as the plates are close together)?

Accepted Answer

The field depends only on the charge-to-area ratio, not the shape.

Electric Fields and Parallel Plate Capacitors: Study Notes

Study Guide - Practice Questions

Study Guide - Flashcards