Q: A $$100\ \Omega$$ resistor is made from a material with resistivity $$\rho = 1.7 \times 10$$^{-8}$$\ \Omega \cdot m$$ and length $$L = 2\ m. $$What is the cross-sectional area $$A of $$the resistor?

$$A = 3.4 \times 10$$^{-7}$$\ m^2$

Question 1

A resistor with resistance $$R is $$connected to a battery with emf $$\varepsilon$$ and internal resistance $$r. $$What is the current $$I$$ flowing through the resistor?

Accepted Answer

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

Question 2

Which of the following best describes the function of a capacitor in a defibrillator circuit?

Accepted Answer

It stores electric energy and releases it rapidly as a pulse.

Question 3

Given three resistors $$R_1 = 2$$\ \Omega$$, R_2$ = 3\ \Omega$$, and $$R_3 = 6$$\ \Omega$$ connected in parallel, what is the equivalent resistance R$$_{eq}$$?

Accepted Answer

$$R_{eq} = 1\ \Omega$$

Question 4

A light bulb is modeled as a resistor. If the voltage across it is doubled, what happens to the power dissipated by the bulb?

Accepted Answer

It quadruples.

Question 5

Which of the following statements about ideal wires in a circuit is correct?

Accepted Answer

They have zero voltage drop regardless of current.

Question 6

A circuit contains a $$10\ \Omega$$ resistor and a $$20\ \Omega$$ resistor in series with a $$12\ 	ext{V}$$ battery. What is the current through the circuit?

Accepted Answer

$$0.3\ 	ext{A}$$

Question 7

Which of the following best describes the role of an inductor in a DC circuit?

Accepted Answer

It opposes changes in current by inducing a back emf.

Question 8

A $$5\ \Omega$$ and a $$10\ \Omega$$ resistor are connected in parallel. What is the equivalent resistance?

Accepted Answer

$$3.33\ \Omega$$

Question 9

Which equation correctly relates the voltage drop across a capacitor to the charge stored on it?

Accepted Answer

$$\Delta V_C = Q/C$$

Question 10

A student builds a circuit with a $$12\ 	ext{V}$$ battery and three identical $$6\ \Omega$$ resistors. Two resistors are in parallel, and this combination is in series with the third resistor. What is the total current supplied by the battery?

Accepted Answer

$$1.2\ 	ext{A}$$

Question 11

Which of the following is a correct application of Kirchhoff’s loop rule?

Accepted Answer

The sum of the voltage drops around any closed loop is zero.

Question 12

A $$9\ 	ext{V}$$ battery is connected to a circuit with a total resistance of $$18\ \Omega. $$What is the power delivered by the battery?

Accepted Answer

$$0.5\ 	ext{W}$$

Question 13

Which material would have the highest resistivity at room temperature?

Accepted Answer

Wood

Question 14

A real battery has an emf $$\varepsilon$$ and internal resistance $$r. If $$the external circuit is shorted (i.e., $$R = 0$$), what is the current?

Accepted Answer

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

Question 15

Which of the following devices is designed to store and quickly release electric energy in a pulse?

Accepted Answer

Capacitor

Question 16

A $$100\ \Omega$$ resistor is made from a material with resistivity $$ho = 1.7 	imes 10$$^{-8}$$\ \Omega \cdot m$$ and length $$L = 2\ m. $$What is the cross-sectional area $$A of $$the resistor?

Accepted Answer

$$A = 3.4 	imes 10$$^{-7}$$\ m^2$

Question 17

Which of the following best describes the effect of increasing temperature on the resistivity of a typical metal conductor?

Accepted Answer

Resistivity increases.

Question 18

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

Accepted Answer

Voltage

Question 19

A $$10\ \mu F$$ capacitor is charged to $$100\ 	ext{V}$$ and then discharged through a patient using a defibrillator. How much energy is delivered?

Accepted Answer

$$0.5\ 	ext{J}$$

PHYS 158 Study Guide: Introduction to DC Circuits and Circuit Elements

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