A voltmeter with resistance rv is connected across the terminals of a battery of emf e and internal resistance r. Find the potential difference vmeter measured by the voltmeter.

V = I (R+r)

Explanation:

According to ohms law, the current (I) passing through a metallic conductor at constant temperature is directly proportional to the potential difference (V) across its end.

Mathematically, V = IR where V is the potential difference

I is the current

R is resistance

Given emf (E) = IRt ... (1)

where E is the emf

Rt is the total equivalent resistance

The external resistance Rv is connected in series with the internal resistance 'r' to give total equivalent resistance Rt = (R+r)

Substituting in equation 1

E = I (R+r)

The equivalent potential difference V = I (R+r)