The current in a simple series circuit is 5.0 amp. When an additional resistance of 2.0 ohms is inserted, the current drops to 4.0 amp. The original resistance of the circuit in ohms was

Options

A. 1.25
B. 8
C. 10
D. 20

Answer

b

Explanation

Let initially resistance in the circuit is `ROmega` Thus, `V = I_(1) R = 5R`....(1)
When addition resistance of `2.0 Omega` is added in the circuit then
`V = 4(R + 2)`...(2)
As voltage across the resistance is same in both cases,
` :. 5R = 4R+ 8 impliesR=8Omega`