Heat is produced at a rate of 250 J per second in an X-ray tube when potential difference of 20 kV is applied between filament and target metal. How much current flows through the tube ? Assume only a small fraction of kinetic energy of electrons is converted into X-rays.

Explanation

If we assume that entire kinetic of electrons is getting converted into heat then :
P=V I `rArr` I=P/V =250/20000=0.0125 A