Question 1

A copper wire of length $$L$$ and cross-sectional area $$A is $$connected to a battery providing a constant voltage $$V. If $$the resistivity of copper is $$\rho$$, what is the expression for the current $$I$$ flowing through the wire?

Accepted Answer

$$I = \dfrac{V A}{\rho L}$$

Question 2

Two resistors, $$R_1 = 4$$\ \Omega$$ and R_2$ = 6\ \Omega$$, are connected in series to a $$12\ V$$ battery. What is the current flowing through the circuit?

Accepted Answer

$$I = 0.8\ A$$

Question 3

Which of the following statements is TRUE about resistors in parallel?

Accepted Answer

The equivalent resistance is always less than the smallest individual resistance.

Question 4

A light bulb is modeled as a resistor of resistance $$R. If $$the voltage across the bulb is doubled, by what factor does the power dissipated in the bulb increase?

Accepted Answer

It increases by a factor of 4.

Question 5

Three identical resistors, each of resistance $$R$$, are connected in parallel. What is the equivalent resistance $$R_{eq} of $$the combination?

Accepted Answer

$$R_{eq} = \dfrac{R}{3}$$

Question 6

A circuit consists of a $$9\ V$$ battery connected to two resistors, $$R_1 = 3$$\ \Omega$$ and R_2$ = 6\ \Omega$$, in parallel. What is the total current supplied by the battery?

Accepted Answer

$$I = 3.0\ A$$

Question 7

If a wire with almost zero resistance is connected in parallel with a resistor in a circuit, what happens to the current through the resistor?

Accepted Answer

It decreases to nearly zero.

Question 8

A $$60\ W$$ light bulb and a $$100\ W$$ light bulb are both rated for $$120\ V$$ and are connected in series to a $$120\ V$$ supply. Which bulb will be brighter and why?

Accepted Answer

The $$60\ W$$ bulb, because it has higher resistance and thus dissipates more power in series.

Question 9

Which equation correctly relates the power dissipated in a resistor to the current and resistance?

Accepted Answer

$$P = I^2$ R$$

Question 10

A circuit contains a $$12\ V$$ battery and two resistors, $$R_1 = 2$$\ \Omega$$ and R_2$ = 4\ \Omega$$, connected in series. What is the voltage drop across $$R_2$$?

Accepted Answer

$$8\ V$$

Question 11

If you add more resistors in parallel to a circuit, what happens to the total current drawn from the battery (assuming the battery voltage is constant)?

Accepted Answer

It increases.

Question 12

A switch is placed in parallel with a light bulb in a circuit. What happens to the brightness of the bulb when the switch is closed?

Accepted Answer

The bulb goes out.

Question 13

Which of the following best explains why the formulas for equivalent resistance in series and parallel are opposite to those for capacitors?

Accepted Answer

Because current divides in parallel for resistors but voltage divides for capacitors.

Question 14

A $$24\ V$$ battery is connected to three resistors in series: $$R_1 = 2$$\ \Omega$$, R_2$ = 4\ \Omega$$, and $$R_3 = 6$$\ \Omega$$. What is the total power dissipated in the circuit?

Accepted Answer

$$8\ W$$

Question 15

In a parallel circuit with two branches, one with resistance $$2\ \Omega$$ and the other with $$8\ \Omega$$, which branch will carry more current and why?

Accepted Answer

The $$2\ \Omega$$ branch, because it has less resistance.

Question 16

A resistor dissipates $$10\ W of $$power when a current of $$2\ A$$ flows through it. What is the resistance of the resistor?

Accepted Answer

$$2.5\ \Omega$$

Question 17

If the resistance in a circuit is doubled while keeping the voltage constant, what happens to the current?

Accepted Answer

It is halved.

Question 18

Which of the following is the correct unit for electrical power?

Accepted Answer

Joule per second ($$J/s)$$

Question 19

A battery supplies a constant voltage $$V to a $$circuit with total resistance $$R. If $$the resistance suddenly decreases, what happens to the rate at which energy is dissipated in the circuit?

Accepted Answer

It increases.

Question 20

Which of the following best describes the physical meaning of electric current?

Accepted Answer

The net flow of charge through a cross-sectional area per unit time.

Electric Current, Resistance, and Energy in Circuits: Series and Parallel Elements

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