Question 1

Which of the following best describes a direct current (DC) circuit?

Accepted Answer

A circuit in which potentials and currents are constant over time.

Question 2

Kirchhoff's junction law is based on which fundamental physical principle?

Accepted Answer

Conservation of charge

Question 3

A battery supplies a constant voltage $$\varepsilon to a $$resistor $$R. $$What is the current $$I in $$the circuit?

Accepted Answer

$$I = \frac{\varepsilon}{R}$$

Question 4

Which of the following statements about resistors in series is correct?

Accepted Answer

The equivalent resistance is the sum of the individual resistances.

Question 5

If three identical lightbulbs are connected in parallel to a battery, which of the following is true?

Accepted Answer

Each bulb receives the same voltage as the battery.

Question 6

A 100 W lightbulb is connected to a 120 V outlet. What is the current drawn by the bulb?

Accepted Answer

$$I = \frac{100}{120} A$$

Question 7

Which property of a real battery causes its potential difference to be slightly less than its emf when supplying current?

Accepted Answer

Internal resistance

Question 8

In an RC circuit, the time constant $$	au is $$given by:

Accepted Answer

$$	au = RC$$

Question 9

Which of the following materials are considered ohmic?

Accepted Answer

Wires and resistors

Question 10

The equivalent resistance $$R_{eq}$$ for two resistors $$R_1$$ and $$R_2 in $$parallel is:

Accepted Answer

$$R_{eq} = \frac{R_1$ R_2$}{R_1$ + R_2$}$$

Question 11

A 4000 W electric water heater runs for 10 hours. How much energy does it use in kilowatt-hours (kWh)?

Accepted Answer

40 kWh

Question 12

Which of the following is true about the current in a series circuit with three resistors?

Accepted Answer

The current is the same through all resistors.

Question 13

In a parallel circuit, what is the same for all resistors?

Accepted Answer

Potential difference (voltage)

Question 14

A capacitor in an RC circuit is initially charged to $$Q_0. $$After a time $$t = 	au$$, what is the charge on the capacitor?

Accepted Answer

$$Q = Q_0$ e$$^{-1}$$

Question 15

Which of the following best explains why a 60 W lightbulb has a higher resistance than a 100 W lightbulb when both are rated for 120 V?

Accepted Answer

Because $$R = \frac{V^2$}{P}$$, so lower power means higher resistance for the same voltage.

Question 16

A circuit contains a 12 $$\Omega$$ and a 6 $$\Omega$$ resistor in series with a 12 V battery. What is the current in the circuit?

Accepted Answer

$$I = 0.5 A$$

Question 17

Which law states that the sum of all potential differences around a closed loop is zero?

Accepted Answer

Kirchhoff's loop law

Question 18

If a resistor dissipates power $$P$$ when a current $$I$$ flows through it, which equation correctly relates $$P$$, $$I$$, and $$R$$?

Accepted Answer

$$P = I^2$ R$$

Question 19

A circuit is grounded at a certain point. What does this mean for the potential at that point?

Accepted Answer

The potential is set to zero volts.

Question 20

In an RC circuit, if the resistance is decreased while keeping the capacitance constant, what happens to the time constant $$	au$$?

Accepted Answer

$$	au$$ decreases

Chapter 28: Fundamentals of Electric Circuits

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