E.m.f. and internal resistanceEdexcel A-Level Physics: Mind map

Exam questions on E.m.f. and internal resistance

1. A cell of e.m.f. 1.5 V and internal resistance 0.50 Ω is connected in series with a 2.5 Ω resistor and a switch.
   Calculate the energy transferred as thermal energy in the internal resistance of the cell in 60 s.2 marks
2. A student measures the terminal p.d. V of a battery for different currents I drawn from it, using a variable resistor. She plots V against I and draws a straight line of best fit. The line meets the V axis at 6.2 V and has a gradient of −0.80 V A⁻¹.
   Explain why the terminal p.d. of the battery is less than its e.m.f. when a current is drawn.2 marks
3. A 12 V car battery has an internal resistance of 0.020 Ω. The headlamps are connected across the battery terminals. When the driver starts the engine, the starter motor draws a current of 150 A from the battery.
   Calculate the terminal p.d. of the battery while the starter motor is operating.3 marks