Question 1

A charged body creates an electric field in the space around it. If a test charge $$q_0 is $$placed at point $$P$$ near a charged body $$A$$, what is the correct expression for the electric field $$\vec{E} at $$point $$P$$ due to $$A$$?

Accepted Answer

$$\vec{E} = \frac{\vec{F}_0}{q_0$}$$

Question 2

Which statement best describes the direction of the electric field produced by a positive point charge?

Accepted Answer

The field points radially outward from the charge.

Question 3

Refer to the diagram with Gaussian surfaces $$S_1$$ through $$S_5. $$For which two surfaces is the total electric flux zero?

Accepted Answer

S1 and S5

Question 4

A test charge $$q_0$$ moves from point $$a to $$point $$b$$ along a straight line extending radially from a charge $$q. If $$the distances are $$r_a$$ and $$r_b$$, what is the work done by the electric field?

Accepted Answer

$$W = \frac{q_0$ q}{4\pi \$$varepsilon_0$$} \left( \frac{1}{r_a} - \frac{1}{r_b} \right)$$

Question 5

What is the electric potential energy $$U of a $$point charge $$q_0 in $$the presence of a collection of charges $$q_1$$, $$q_2$$, $$q_3$$, ...$$ at distances r_1$, r_2$, r_3$, ...$$?

Accepted Answer

$$U = \frac{q_0$}{4\pi \$$varepsilon_0$$} \sum_i \frac{q_i}{r_i}$$

Question 6

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

Accepted Answer

Electric field lines are always perpendicular to equipotential surfaces.

Question 7

At all points on the surface of a conductor, the electric field must be:

Accepted Answer

Perpendicular to the surface

Question 8

For a parallel-plate capacitor with plate area $$A$$ and separation $$d$$, what is the expression for its capacitance $$C$$?

Accepted Answer

$$C = \frac{\$$varepsilon_0$$ A}{d}$$

Question 9

When capacitors are connected in parallel, the equivalent capacitance is:

Accepted Answer

$$C_{eq} = C_1$ + C_2$ + C_3$ + \cdots$$

Question 10

When capacitors are connected in series, the equivalent capacitance is:

Accepted Answer

$$\frac{1}{C_{eq}} = \frac{1}{C_1$} + \frac{1}{C_2$} + \frac{1}{C_3$} + \cdots$$

Question 11

In a parallel-plate capacitor, if the plate area is doubled and the separation is tripled, what happens to the capacitance?

Accepted Answer

$$C_{new} = \frac{2}{3} C$$

Question 12

A current $$I$$ flows through a wire with cross-sectional area $$A. $$What is the correct expression for current in terms of charge $$Q$$ and time $$t$$?

Accepted Answer

$$I = \frac{\Delta Q}{\Delta t}$$

Question 13

The equivalent resistance for resistors in series is:

Accepted Answer

$$R_{eq} = R_1$ + R_2$ + R_3$ + \cdots$$

Question 14

The equivalent resistance for resistors in parallel is:

Accepted Answer

$$\frac{1}{R_{eq}} = \frac{1}{R_1$} + \frac{1}{R_2$} + \frac{1}{R_3$} + \cdots$$

Question 15

Kirchhoff's loop rule states that:

Accepted Answer

The algebraic sum of the potential differences in any loop must equal zero: $$\sum V = 0$$

Question 16

In a circuit element, the power input $$P is $$given by:

Accepted Answer

$$P = V_{ab} I$$

Question 17

If a resistor has color bands: red, violet, yellow, and gold, what is its resistance and tolerance?

Accepted Answer

27 	imes $$10^4$$ \Omega, 5\%

Question 18

In a real emf device, what is the direction of current relative to the potential?

Accepted Answer

Current flows from lower to higher potential inside the emf device.

Question 19

If an electric field is produced inside a conductor that is not part of a complete circuit, what happens to the current after a very short time?

Accepted Answer

The current stops completely because the net electric field becomes zero.

Electric Fields, Potential, Capacitance, Current, and Circuits: Core Concepts and Applications

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