Copper and silicon is cooled from 300 K to 60 K , the specific resistance

If specific resistance of a potentiometer wire is 10^-7$$\Omega $$ m and current flow through it is 0.1 amp., cross-sectional area of wire is 10^$$-$$6 m² then potential gradient will be

The net resistance of the circuit between A and B is

A car battery of emf 12 V and internal resistance $$5 \times {10^{ - 2}}$$ $$\Omega $$., receives a current of 60 amp, from external source, then terminal potential difference of battery is