Question 1

Two resistors of 2 Ω and 3 Ω are connected in series. What is the equivalent resistance?

Accepted Answer

5 Ω. In series, resistances add, so R = 2 + 3 = 5 Ω. The same current flows through each series resistor. Series connection increases total resistance and reduces current for a fixed voltage.

Question 2

Two resistors of 6 Ω and 3 Ω are connected in parallel. What is the equivalent resistance?

Accepted Answer

2 Ω. For parallel resistors, 1/R = 1/6 + 1/3 = 1/6 + 2/6 = 1/2 so R = 2 Ω. In parallel, the voltage across each branch is the same. Equivalent resistance in parallel is always less than the smallest branch resistance.

Question 3

A 12 V cell with internal resistance 1 Ω is connected to a 5 Ω resistor. What current flows in the circuit?

Accepted Answer

2 A. Total resistance is R + r = 5 + 1 = 6 Ω, so I = E/(R+r) = 12/6 = 2 A. Internal resistance reduces the current compared to an ideal cell. Terminal voltage becomes lower than emf when the cell delivers current.

Question 4

A current of 3 A flows through a 4 Ω resistor. What power is dissipated in the resistor?

Accepted Answer

36 W. Power in a resistor is P = I^2R, so P = 3^2 × 4 = 36 W. This electrical power is converted mainly into heat in the resistor. The unit watt equals joule per second.

Question 5

A 10 V supply is connected across 2 Ω and 3 Ω in series. What is the potential difference across the 3 Ω resistor?

Accepted Answer

6 V. In a series divider, V across 3 Ω is V = 10 × 3/(2+3) = 6 V. Series resistors share voltage in proportion to their resistances. A potential divider is widely used to obtain a desired fraction of a voltage.

Circuits — Set 1