1.1. Explain why the electromotive force (e.m.f) of a cell with internal resistance may be more than the terminal potential difference (p.d.) of the cell.

1.2. Compare the definitions of e. m .f and p. d.

1.3. For a cell, explain the term internal resistance.

1.4. A battery of e.m.f 1508 V and internal resistance r is connected to a resistor A, as shown in Fig 1.1. 

Fig 1.1

The current in resistor A is 400 mA and the power dissipated by it is 600 W. 

Calculate r of the battery.