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Q2. A relay coil has a resistance of 400 Ω and the current required to operate the relay is 45 mA. When the coil is connected to a 24 V d.c. supply it takes 30 ms for the relay to operate.

(a) Calculate EACH of the following:

(i) The steady-state relay current; (2)

(ii) The time-constant of the coil; (4)

(iii) The inductance of the coil. (4)

(b) To increase the operating time for the relay, a 40 Ω resistor is connected in series with the coil. Determine the new operating time for the relay. (6)