question_answer 2)

A battery of e.m.f. 10 V and internal resistance 3 is connected to a resistor. If the current in the circuit is 0.5 A, what is the resistance of the resistor? What is the terminal voltage of the battery when the circuit is closed?  

Answer:

Using     E = V + Ir,                 we get  E = IR + Ir                 i.e.,                        Again using E = V + Ir, we get                 V = E ? Ir = 10 ? 0.5 x 3                 = 10 ? 1.5 = 8.5 V.                 Shortcut. Here V = IR = 0.5 x 17                 = 8.5 V.