groth and decay of current

The LR Series Circuit

 

When we close the switch the electric current the circuit doesn't go instantaneously to it's maximum value, but it slowly grows to the maximum current.

Similarly when the maximum current is attained and we open the switch the current doesn't go to zero, instantaneous, but decays to zero.

Transient Curves for a LR Series Circuit

 

Solution Kirchoff's voltage law for a series LR circuit yields the following expression for electric current in the circuit.

I = (V/R)(1 - e ^-t/τ),   

 

where τ = L/R is the time constant, as it depends upon L and R values it'll be constant for a given circuit.

It represents the time for the current to attain 63% of maximum current.

Regards,

Team,

TopperLearning.