Question

A voltmeter of resistance 20000 reads 5v. to make it read 20 v the extra resistance required is

Answer 1

Here is your answer u looking for....

5v = 20,000 ohms

1V =20,000/5

1v = 4,000 ohms

Now,
20V = 4,000*20
= 80,000 ohms....

hope its help...!!!

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