The time constant of an `LR` circuit represents the time in which the current in the circuit

Options

A. Reaches a value equal to about 37% of its final value
B. Reaches a value equal to about 63% of its final value
C. Attains a constant value
D. Attains 50% of the constant value

Answer

B

Explanation

`i=i_(0)(1-e^(-t//tau))" "[becausetau=L/R]`
`i=i_(0)(1-1/e)" "["as "t=tau]`
`i_(0)((e-1)/e)=0.63i_(0)" "[becausee=2.71]`