Question

Consider an electromagnet (e.g. in a relay) that is operated at 50 A. If the inductance of the coil is 100 H and the time to switch-off the current is 1 ms, what voltage will be developed across its terminals?

Answer 1

Answer:

5 x 10⁶ volts

Explanation:

$i_{o}$ = Initial value of current = 50 A

$i_{f}$ = Final value of current = 0 A

Δt = time taken = 1 ms = 0.001 s

$V$  = Voltage developed across the terminals

Voltage developed across the terminals is given as

$V = \frac{L(i_{f} - i_{o})}{\Delta t}$

$V = -\frac{(100)(0 - 50)}{0.001}$

$V$  = 5 x 10⁶ volts