Q: A charge of $$+2\ \mu\mathrm{C} is $$fixed at the origin. What is the magnitude of the electric field at a point $$0.5\ \mathrm{m}$$ away on the $$x-$$axis?

$$3.6 \times 10^4$\ \mathrm{N/C}$$

Question 1

A lithium atom has 3 electrons, 3 protons, and 3 neutrons. What is the net charge in Coulombs on the atom?

Accepted Answer

$$0\ \mathrm{C}$$

Question 2

Two charges $$Q_1$$ and $$Q_2$$ are placed at the vertices of an equilateral triangle with side $$a. If$$ $$Q_1 = +2$$\ \mu\mathrm{C}$$ and Q_2$ = -2\ \mu\mathrm{C}$$, what is the direction of the net electric field at the third vertex?

Accepted Answer

Perpendicular to the base, pointing toward the midpoint

Question 3

A charge of $$+2\ \mu\mathrm{C} is $$fixed at the origin. What is the magnitude of the electric field at a point $$0.5\ \mathrm{m}$$ away on the $$x-$$axis?

Accepted Answer

$$3.6 	imes 10^4$\ \mathrm{N/C}$$

Question 4

An electroscope is positively charged by touching it with a glass rod rubbed with silk. The electroscope leaves spread apart and remain so after the rod is removed. What does this indicate?

Accepted Answer

The leaves have retained the charge; the rod is no longer in contact.

Question 5

A point charge $$Q is $$placed $$0.2\ \mathrm{m}$$ above a large conducting sheet with surface charge density $$\sigma = 1.5 	imes 10$$^{-6}$$\ \mathrm{C/m}^2. $$What is the force on the charge due to the sheet?

Accepted Answer

$$F = Q \sigma / (2 \$$varepsilon_0$$)$$

Question 6

A charge $$Q_1 = +10$$\ \mu\mathrm{C}$$ is fixed at (0$$,0)$$ and a charge Q_2$ = -5\ \mu\mathrm{C} is $$fixed at $$(0,4). $$What is the direction of the net electric field at the point $$(3,0)$$?

Accepted Answer

At an angle between the positive $$x- $$and negative $$y-$$axes

Question 7

Consider two charges positioned as shown: $$+Q at$$ $$(0,0)$$ and $$-Q at$$ $$(a,0). In $$which region(s) is the electric field zero?

Accepted Answer

At a point to the left of $$+Q$$

Question 8

A charge $$Q is $$distributed uniformly along a long straight line of length $$L. $$The electric field at a distance $$r$$ from the center of the line (where $$r \gg L) is $$approximately:

Accepted Answer

$$E = \dfrac{Q}{4 \pi \$$varepsilon_0$$ r^2$}$$

Question 9

The electric field lines for two point charges $$Q_1$$ and $$Q_2$$ are shown. If the field lines are denser around $$Q_1$$ than $$Q_2$$, what can you conclude?

Accepted Answer

$$|Q_1$| \u003e |Q_2$|$$

Question 10

A charge $$+q is $$placed at the origin. What is the direction of the electric field at the point $$(1,1)$$?

Accepted Answer

Along the line $$y = x$$, away from the origin

Question 11

A positively charged rod is brought near, but does not touch, a neutral metal sphere. What happens to the charges in the sphere?

Accepted Answer

Negative charges move toward the rod, positive charges move away

Question 12

Which of the following statements about electric field lines is correct?

Accepted Answer

They indicate the direction of the force on a positive test charge

Question 13

A charge $$Q is $$placed at the center of a cube. What is the total electric flux through all six faces of the cube?

Accepted Answer

$$\dfrac{Q}{\$$varepsilon_0$$}$$

Question 14

A charge $$Q is $$placed near a grounded conducting plane. The force on the charge is equivalent to:

Accepted Answer

The force between $$Q$$ and an image charge $$-Q at $$the mirror position

Question 15

A charge $$Q is $$placed at a distance $$d$$ from an infinite plane with surface charge density $$\sigma. $$What is the electric field at the location of the charge due to the plane?

Accepted Answer

$$E = \dfrac{\sigma}{2\$$varepsilon_0$$}$$

Question 16

Which of the following best describes the principle of superposition for electric fields?

Accepted Answer

The net electric field is the vector sum of the fields due to individual charges

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