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Q1. A 120 mF capacitor is charged through a resistance from a 12 V d.c. supply and the instantaneous charging current at switch on is 2.55 mA.

(a) Calculate EACH of the following:

(i) The value of the charging resistance:

(ii) The time constant;

(iii) The voltage across the capacitor after 2 s of charging;

(iv) The energy stored after 2 s.

(b) After 2.5 s of charging the supply is switched off and the capacitor is discharged through a 1.2 kW resistor. Calculate EACH of the following:

(i) The new time constant;

(ii) The voltage across the capacitor after 124ms;

(iii) The discharge current at 124 ms.