Question 1

According to Kirchhoff’s loop rule, what is the algebraic sum of the potential differences (including emfs and resistive elements) around any closed loop in a circuit?

Accepted Answer

$$\sum V = 0$$

Question 2

In the sign convention for emfs, what is the correct sign for the emf when traveling from the negative to the positive terminal of a battery?

Accepted Answer

It is positive: $$+\mathcal{E}$$

Question 3

You are analyzing a circuit with two batteries in series, each with its own internal resistance. What is the total emf and total internal resistance of the combination?

Accepted Answer

Total emf: $$\mathcal{E}_1 + \mathcal{E}_2$$, Total resistance: $$r_1$$ + $$r_2$$

Question 4

A voltmeter is used to measure the voltage across a resistor in a circuit. How should it be connected, and what is the ideal resistance of the voltmeter?

Accepted Answer

Connected in parallel with infinite resistance

Question 5

In the circuit shown in the second image, what is the equivalent resistance of the two resistors (3 $$\Omega$$ and 6 $$\Omega) in $$parallel between points e and d?

Accepted Answer

$$R_{eq} = 2\ \Omega$$

Question 6

If you traverse a resistor in the direction of the current, what is the sign of the potential difference across the resistor?

Accepted Answer

Negative: $$-IR$$

Question 7

A 12 V battery is connected in series with a 50 $$\Omega$$ resistor and a 100 $$\muF $$capacitor. How long does it take for the capacitor to reach 90% of its maximum charge?

Accepted Answer

$$t = -RC \ln(0.10)$$

Question 8

Which of the following best describes the time constant $$	au in an RC $$circuit?

Accepted Answer

$$	au = RC$$

Question 9

When charging a capacitor in an RC circuit, what is the expression for the charge on the capacitor as a function of time?

Accepted Answer

$$q(t) = Q_{max} (1 - e$$^{-t/RC}$$)$$

Question 10

A circuit contains a resistor and a capacitor in series with a battery. Immediately after the switch is closed, what is the current in the circuit?

Accepted Answer

$$I_0$$ = \frac{\mathcal{E}}{R}$$

Question 11

Which of the following statements about ammeters is correct?

Accepted Answer

An ideal ammeter has zero resistance and is connected in series

Question 12

In a multi-loop circuit, if the calculated current comes out negative, what does this indicate?

Accepted Answer

The actual current flows opposite to the assumed direction

Question 13

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

Accepted Answer

The sum of currents entering a junction equals the sum of currents leaving

Question 14

A battery with emf $$\mathcal{E}$$ and internal resistance $$r is $$connected to an external resistor $$R. $$What is the terminal voltage of the battery?

Accepted Answer

$$V = \mathcal{E} - I r$$

Question 15

In a circuit with multiple batteries in series, what is a practical disadvantage of increasing the number of batteries?

Accepted Answer

The total internal resistance increases, reducing efficiency

Question 16

Which of the following best describes the current in an RC circuit as the capacitor charges over time?

Accepted Answer

$$I(t) = \frac{\mathcal{E}}{R} e$$^{-t/RC}$$

Question 17

A student wants to measure both the current through and the voltage across a resistor in a circuit. How should the ammeter and voltmeter be connected?

Accepted Answer

Ammeter in series, voltmeter in parallel

Question 18

If a circuit contains a resistor of $$R_1 = 4$$\ \Omega$$ in series with a parallel combination of R_2$ = 6\ \Omega$$ and $$R_3 = 3$$\ \Omega$$, what is the total resistance?

Accepted Answer

$$R_{total} = 4 + 2 = 6\ \Omega$$

Question 19

Which of the following is true about the voltage across a fully charged capacitor in a series RC circuit?

Accepted Answer

It equals the emf of the battery: $$V = \mathcal{E}$$

Week 5 Lec. 2

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