Question

An inductor (0.2 Henry) and a resistor (2ohms) are connected in series with a battery of EMF 5.0 volts.

a) Draw the circuit (don't forget the switch)

b) At time t=0 and time= infinity find the current that passes through the battery

c) What's the time constant for the circuit?

d) What's the back EMF provided by the inductor at t= 1.0 sec?

e) What's instantaneous energy saved in the inductor at time t= 1.0 sec?

f) What is the total magnetic flux that is coupled with the inductor at t= 1.0 sec?

Answer 1

b)

at time t = 0

current passing through the circuit would be "0" amperes, since the inductor would oppose sudden change in current by producing equal value of EMF which is applied across it, hence no current flows through it initially at t = 0

at t -> infinity the inductor would be in steady state and would offer 0 resistance to the flow of current through it since the current is not changing, hence the value of current in circuit at t tending to infinity would be I = V/R

I = 5/2 = 2.5 amperes.

c)

time constant for the circuit would be LR = 0.2* 2 = 0.4 seconds

d)

voltage across the inductor is given by volts

where voltage at t = 0, t = time, = time constant

hence back EMF V at t= 1 sec, V = = 0.41 volts

e )

energy = E = 0.526 joules

here I(t) =

f)

magnetic flux = L*I(t)

flux = 0.2 * 2.29 = 0.458 weber/