Which one of the following combinations of open circuit

Home » Network Theory » Network Elements and the Concept of Circuit » Question

Which one of the following combinations of open circuit voltage and Thevenin's equivalent resistance represents the Thevenin's equivalent of the circuit shown below in the figure?

1. 1 V, 10 Ω
2. 1 V, 1 kΩ
3. 1 mV, 1 kΩ
4. 1 mV, 10 Ω

Correct Option: A

Calculation for Rth:
Let an imaginary voltage source (say 5V) is applied through the terminal a and b, and assume that current I is flowing due to this source so R_th will be the ratio of V/I.

Apply KVL 5 = 1000 I₁

I ₁ =		-	5
			1000

I = 99 I₁ + I₁ = 100 I₁

R_th =		I_C	=	- 5		5	= 10 Ω (sign neglected)
		I		100 I₁		100(5 / 10000)

Calculation for V_th

Apply KCL at node A
I₁ + 99 I₁ = 0
I ₁ = 0
Now, the circuit becomes

I ₁ = 0, shows that there will be no drop across 1 kΩ resistance.
Hence V_th = 1 V