Shown in the figure is an R-L circuit. Just after the Key (K) is closed
the current in the circuit is E/R
no potential drop across the resistor
potential drop across the inductor is E/2
heat is dissipated in the circuit in the resistance
The current in the circuit at the instant of closing the Key (K) is equal to io. Current at any time in transient state is given by
Putting t = 0, i = 0
Potential drop across resistor is zero
The voltage drop across the inductor is
that oppose the applied emf E
numerically. Since the circuit current is zero, the heat loss (proportional to
) will be zero