How Accurate is the Calculated Inductance of 74mH in a Series RL Circuit?

[snipaj9696]

I would like to verify these answers please..

What is the inductance of a series RL circuit in which R=1.0 K ohms if the current increases to 1/3 of it's final value in 30 Ms (M is the greek symbol Mu).

Is the answer 30 (none of these) or is it 74mH?? I calculated 74mH

i(t) = I (1-1/e^t/τ)

given i(t) = 1/3*I and t =30uS and τ =L/R

so,,substitutin these values

we get t/τ = 0.41

30*10^-6 / τ = 0.41

τ ˜ 74 μ sec

L/R ˜ 74usec

R = 1K

so,,L ˜74mH




The choices for answers are.

1.) 49
2.) none of these
3.) 99
4.)74
5.) 62

thankyou!

 

[quantumdude]

I get 74mH too.

 

[Moetasim]

I would like to verify these answers as well. Based on your calculations, it seems that the correct answer is 74mH. However, it is always important to double check calculations and consider any potential sources of error. I would recommend checking your calculations and possibly consulting with a colleague or referring to a reliable source to confirm the answer. It is also important to consider the units and ensure they are consistent throughout the calculations. Thank you for bringing this to my attention.