Question

Calculate the number of electrons drifting per second through the filamentof 100w

Answer 1

We know that rate of doing work is power .

also energy E = I2R where I is the current and R is the resistance.

From ohm’s law ,we know that V = IR

Hence E = I V

In the given question V = 220V

Also current is charge per unit time

Hence I = q/t , here q = ne where n is the number of electrons which we need to calculate and e is the charge given as 1.6*10-19C

Also t = 1sec as given in the question.

Power P = 100W

Hence P *t = I2R

100 = 220 * n *1.6*10-19

Solving for n we get n = 2.84*1018