# LR circuits - time constant meaning

If you have a huge time constant in LR circuits, does this mean it takes a long time to discharge and lose all current in circuit?

Similarly, if you have a tiny time constant in LR circuits, does this mean it takes a very short time to discharge circuit?

• LR circuits do not contain capacitors. – sammy gerbil Mar 18 '17 at 19:00
• Apologies! I meant, discharge & lose all current in circuit? – Marie R Mar 18 '17 at 19:02
• Yes, that's it. More info en.wikipedia.org/wiki/Time_constant – JMLCarter Mar 18 '17 at 19:08

One time constant specifies how long it takes to see 63% of the total change, as given by $1-e^{-1}$. This means that a long time constant requires a long time to see 63% of the total change, while a short time constant requires a short time to see 63% of the total change. Note that the time-constant concept is used because the exponential decay function never quite gets to zero mathematically.