A voltmeter reads the potential difference across the terminals of an old battery as `1.40 V`, while a potentiometer reads its voltage to be `1.55 V`. The voltmeter resistance is `280 Omega`.

Options

A. the emf of the battery is 1.4 V
B. the emf of the battery is 1.55 V
C. the internal resistance r of the battery is `30 Omega`
D. the internal resistance r of the battery is `5 Omega`

Answer

B, C