For the adjoining circuit diagram, the readings of ammeter and voltmeter are 2A and 120 V respectively. If the value of R is `75 Omega`, then the voltmeter resistance will be

Options

A. `100 Omega`
B. `150 Omega`
C. `300 Omega`
D. `75 Omega`

Answer

C

Explanation

`V_(AB)=(l-l_(g))R=l_(g).G`
where, G=voltmeter(resistance)
`V_(AB)=120, l=2, R=75`
`implies 120=(2-l_(g))75 implies l_(g)=0.4A`
Now, `V_(AB)=l_(g)G implies G=(120)/(0.4)=300 Omega`