Q12. A capacitor of 100 µF is charged for 5 secs from a 100 volt d.c. supply via a resistor of 100 kn.
(a) Calculate EACH of the following:
(i) The voltage across the capacitor at the end of this period;
(ii) The energy stored in the capacitor at the end of this period.
(b) At the end of this period the capacitor is disconnected and a second capacitor of 100 µF already charged to 70 volts is connected in parallel with it. Calculate EACH of the following:
(i) The final steady state voltage across the pair;
(ii) The energy stored by the pair of capacitors.
Q7. Fig Q3 shows a basic voltage stabilising circuit using a Zener diode and a series resmor. The Zener diode has a breakdown voltage of 12 V and is rated at 2 W maximum dissipation. The diode requires a minimum reverse current of 2 mA for satisfactory stabilisation and its slope resistance is negligible
Calculate EACH of the following:
(a) The maximum safe input voltage when the output current is zero;
(b) The maximum output current for satisfactory stabilisation when the input voltage is 18 volts.
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