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Q2. When connected to a 20 V d.c supply a relay starts to operate 0.52 ms after switching on the supply, at which time the instantaneous current is 200 mA. The relay coil has a time constant of 5 ms.

(a) Calculate EACH of the following:

(i) The final steady relay current; (6)

(ii) The resistance and inductance of the relay coil. (4)

(b) To increase the operating time a 40 Ω resistor is connected in series with the relay coil.

Calculate the new time delay assuming the instantaneous current is still 200 mA. (6)