when you press one of the buttons on a small calculator a 35

when you press one of the buttons on a small calculator, a 3.5 volt battery provides a small constant current of 50 uA for 400 ms. determine the following :-

A) how many electrons flow in that time ?

B) the electrical potential energy U (in uJ) produced by the battery (assume an ideal battery)

Solution

Here ,

voltage , V = 3.5 V

current , I = 50 uA

time , t = 400 ms

a)

number of electrons passed = charge/charge on electron

number of electrons passed = 50 *10^-6 * 400 *10^-3/(1.602 *10^-19)

number of electrons passed = 1.248 *10^14

the number of electrons passed is 1.248 *10^14

b)

energy produced by battery= V * I * t

energy produced by battery = 3.5 * 50 uA * 400 *10^-3 V * s

energy produced by battery= 70 uJ

the energy produced by battery is 70 uJ