Question

the resistance of the voltmeter is 10000 ohm and that of the ammeter is 20ohm .if the reading of the ammeter is 12 volt then the value of R is​

Answer 1

In the circuit shown the resistance of voltmeter is 10,000 ohm and that of ammeter is 20 ohm.
The ammeter reading is 0.10 Amp and voltmeter reading is 12 volt. Then R is equal to 
(A) 122 Ω
(B) 140 Ω
(C) 116 Ω
(D) 100 Ω
Correct option (D) 100 ohm
  Explanation: V = i(r + R) 12
= 0.1(20 + r)
⇒ r = 100 ohm

Answer 2

Given:

Current,

i = 0.10

V = 12 volt

Ammeter,

r = 20 Ω

To Find:

Value of R = ?

Solution:

As we know,

⇒  $V=i(r+R)$

⇒  $12=0.1(20+R)$

⇒  $12=2+0.1R$

⇒  $12-2=0.1R$

⇒  $10=0.1R$

⇒  $R=\frac{10}{0.1}$

⇒  $R=100 \ ohm$

So that the value of R will be "100 ohm".