Question

On a six fold increase in external resistance of a circuit the voltage across the terminals of the battery has increased from 5 V to 10 V. The emf of battery is
A. 15 V
B. 18 V
C. 12.5 V
D. 11 V

Answer 1

Correct Answer - C
(E-V)/(V)R=r implies (E-5)/(5) R=r`
`(E-10)/(10)6R=r`
` Equating Eqs. (i) and (ii), we get
`(E-5)/(5)R=(E-10)/(10)6R implies E-5=3E-30`
`2E=25 implies E=12.5V`