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Q2.  A relay has a time constant of 5 ms and starts to operate 0.52 ms after connection to a 20 V D.C. supply.

(a) If the instantaneous current is 200 mA, calculate EACH of the following:

(i) The final steady state 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 operating time for the relay assuming the instantaneous current is 200 mA. (6)