Question

Two voltmeter of resistance 15 kilo ohm and 20 kilo ohm are connected in series across 200v supply. Both meter are 0 to 300v range. Find the reading of the voltmeter. ​

Answer 1

Answer:

The voltage source and the two voltmeters are connected in series here, so then the current must be constant.

Let me find the current I first.

By Ohm’s law, I = 240 / ( 15000 + 5000 ) = 240 / 20000 = 0.012 A.

Hence again by ohm’s law,

Voltage reading across voltmeter 1 is 0.012 * 15000 = 180 v.

Voltage reading across voltmeter 2 is 0.012 * 5000 = 60 v.

Method II :-

By voltage division rule,

Voltage reading across voltmeter 1 is = ( 240 * 15000 ) / ( 20000 ) = 180 v.

Voltage reading across voltmeter 2 is = ( 240 * 5000 ) / ( 20000 ) = 60 v.

This can be verified by Kirchoff’s voltage law ( Sum of the voltage sourcing = Sum of voltage drops ) as,

240 v = 180 + 60 v =240