Question

A voltmeter with resistance 20000 ohm reads 5 v. to make it read 20 v what extra resistance is required

Answer 1

60000extra ohm is req

Answer 2

R=20000ohm

Potential difference (V)=5V

I(current)=?

Using ohm's law

V=IR

5=20000I

I=5/20000C

now if V=20V

I will be constant i.e. 5/20000C

using V=IR

20=5R/20000

R=400000/5 i.e 80000ohm