Question 1

Two resistors, $R_1 = 4$ ohm and $R_2 = 6$ ohm, are connected in series. What is the total (equivalent) resistance?

Accepted Answer

10 ohm — In series, resistances simply add: $R_s = R_1 + R_2 = 4 + 6 = 10$ ohm.

Question 2

Two resistors, $R_1 = 6$ ohm and $R_2 = 3$ ohm, are connected in parallel. Calculate the equivalent resistance using $\frac{1}{R_p} = \frac{1}{R_1} + \frac{1}{R_2}$. Give your answer in ohm.

Accepted Answer

2 — $\frac{1}{R_p} = \frac{1}{6} + \frac{1}{3} = \frac{1}{6} + \frac{2}{6} = \frac{3}{6} = \frac{1}{2}$, so $R_p = 2$ ohm.

Question 3

A 12 V battery (assume no internal resistance) is connected across two resistors in series: $R_1 = 2$ ohm and $R_2 = 4$ ohm. Calculate the current in the circuit using $V = IR$ with the total resistance. Give your answer in A.

Accepted Answer

2 — $R_{total} = 2 + 4 = 6$ ohm. $I = \frac{V}{R} = \frac{12}{6} = 2$ A.

Electric Circuits & Electrodynamics

Sample practice questions