If a cell has an emf of 5 V and the value of lost volts is 2 V, what is the current of the resistor?

First, write down what you know. Lost volts = Ir = 2V, Emf = 5V. Next, find the p.d across R using ε = IR + Ir. 5 = IR + 2, IR = 3V. Using V = IR, find the current. 3 = I x 10, I = 0.3. Therefore, I is 0.3 A.