Question

(a) A capacitor of capacitance 220 μF is connected in series with a 150 kΩ resistor, a switch and an ammeter. A d.c. power supply of negligible internal resistance is connected to the circuit as shown below 1 50 kΩ 220HF A stopclock is started and after 10 seconds the switch S is closed Ammeter readings are noted at regular intervals until a time of 80s is shown on the stopclock. The graph below shows how the current in the circuit varies with time. 100 80 60 current/uA 40 20 0 10 20 30 40 50 60 70 80 90 100 time/s (i) Calculate the voltage Vof the d.c. power supply (ii) At what time on the stopclock does the p.d. across the resistor equal 6 V? (iii) What is the p.d. across the capacitor when the p.d. across the resistor is 6 V? (b) A magazine article on the resuscitation of a heart attack victim describes the equipment used. This equipment uses a 16μF capacitor which is charged until the pd. across it is 6kV. The capacitor is then fully discharged to give the heart a shock. The discharge time 5 2 ms. (i) When the capacitor is fully charged, calculate: (A) the charge stored; (B) the energy stored. (ii) Calculate the average current during discharge

Answer 1

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