Question

Calculate the current across the 4 ohm resistor.

(a) 0.86A

(b) 1.23A

(c) 2.22A

(d) 0.67A

The question was asked during an online exam.

My enquiry is from Thevenin’s Theorem topic in division Network Theorems of Basic Electrical Engineering

Answer 1

Correct answer is (a) 0.86A

Best explanation: Thevenin resistance is found by opening the circuit between the specified terminal and shorting all voltage sources.

When the 10V source is shorted, we get:

Rth=(1||2)+3=3.67 ohm.

Vth is calculated by opening the specified terminal.

Using voltage divider, Vth= 2*10/(2+1)=6.67V.

On drawing the Thevenin equivalent circuit, we get Rth, 4 ohm and Vth in series.

Applying Ohm’s law, I=Vth/(4+Rth) = 0.86A.