As part of a class project, you are designing an electromagnetic door closer tha

Question

As part of a class project, you are designing an electromagnetic door closer that makes use of a solenoid actuator. The coil of the actuator has inductance  L. To close the door at a controlled speed, you place the actuator in series with a resistor R = 2500 , a switch, and a dc voltage source V0 = 240 V . After closing the switch, you find that the current through the coil smoothly increases to its steady-state value with a time constant . The steady-state value provides the correct current, but you would like to be half as long.

Part A: What new value should you use for R?

R = _________ ____

Part B: What new value should you use for V0?

V0 = ___________ ______

Explanation / Answer

time constant is T = L/R

to get T/2 = (L/2R)

then the new R is 2R = 2*2500 ohm = 5000 ohm

B) Vo = 240/2 = 120 V

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