Problem 1: A battery has an emf of 12.8 V and supplies a current of 3.2A. What is the resistance of the circuit? How many coulombs leave the battery in 5 minutes?

Solution

Given      emf = 12.8 V                      I = 3.2 A               

                      t = 5 minutes = 5 * 60 = 300 seconds

Required              Resistance of the circuit, R =?                     

                              Charge passed = Q =?

By Ohm’s law                    V = IR . 

Put the values 

 

For finding the amount of charge Q, we use the definition of current.

I = Q/t

Put values and simplify,