Question

When a voltmeter is connected across a 400 ω resistance, it reads 30v, when it is connected across 300 ω resistance, it will read?

Answer 1

hello friend...!!

• According to the question we should calculate the voltage reading when it is connected across 300 ohm resistance.

• In case ( 1 )

Resistance ( R) = 400 ohm
voltage ( V) = 30 v

therefore,

V = I R

implies, I = V / R

I = 30 / 400

I = 3 / 40 -------------( 1 )

in case ( 2 )

it is given R = 300 ohm and we should calculate the voltage and we know I = 3/40

therefore,

V = I R

V = ( 3 / 40 X 300 )

V = 45/2

therefore,

V = 22.5 volt.

_____________________________

Hope it is useful to you..!!

Answer 2

The correct answer to the question is 22.5 volt.

CALCULATION:

As per the question, first the voltmetre is connected across 400 ohm resistance.

The potential is given as V = 30 volt.

The resistance is given as R = 400 ohm.

From Ohm's law, we know that V = IR

Here, I is the current, R is the resistance and V is the potential difference.

The current flowing through the resistor is calculated as -

                            current $I=\frac{V}{R}$

                                              $=\ \frac{30}{400}\ A$

                                              $=\ 0.075\ A$

We are asked to calculate the potential read by voltmetre when it is connected to a resistance of 300 ohm.

Hence, the potential is calculated as -

                            potential  V = IR

                                                = 0.075 A × 300 ohm

                                                = 22.5 volt.                  [ans]