What is the coil current 2ms after being connected to the supply if a coil of inductance 0.5H and resistance 500Omega is connected across a 250V DC supply? (The time constant T of the circuit is 1ms).

1 Answer
May 28, 2018

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For an LR Series circuit as shown in the figure above, the expression for the current I is given as

I(t)=E/R(1-e^(-t/tau))
where time constant tau= L/R and E/R represents the final steady state current in the circuit.

Inserting given values we get

I_"(2 ms)"=250/500(1-e^(-2/1))
=>I_"(2 ms)"=0.43\ A

.-.-.-.-.-.-

We can verify that tau=0.5/500=0.001\ s, as given