Question

A resistor and an inductor are connected in series to a battery. The battery is suddenly removed from the circuit. The time constant for of the circuit represents the time required for the current to decrease to
a) 50% of the original value
b) 75% of the original value
c) 37% of the original value
d) 25% of the original value
e) 63% of the original value

Answer 1

The time constant is how long the current to decrease by 1/e

Answer 2

so its 37% ?

Answer 3

you're looking for a decrease in the value that was 100% so you need 1/e less than 100%

Answer 4

63!!!! :)