In figure circuit section `AB` absorbs energy at the rate of `5.0 W` when a current` i =1.0A` passes through it in the indicated direction.
(a) What is the potential difference between points `A` and `B`?
(b) Emf device `X` does not have internal resistance. What is its emf?
(c) What is its polarity (the orientation of its positive and negative terminals)?

Answer

A, B, C, D

Explanation

Power absorbed by resistor is `i^2R` or `2W`.
Therefore, remaining `3W` is absorbed by the battery (`=Ei`). Hence `E` is `3V` and current of `1 A` enters from the position terminal as shown below.

`V_(AB)=E+ir`
`=E+iR ("here" r=R)`
`=3+(1)(2)=5V`