# Mutual Inductance and wire coils (1 Viewer)

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#### edlin

Hi..I am new here and I am really thankful for any help that I may get I am stuck in a problem of mutual inductance. It seems fairly simple, yet I cannot get the correct answer.

Two coils are close to each other. The first coil carries a time-varying current given by I(t) = (4.60 A) e-0.0250tsin(377 t). At t = 0.800 s, the voltage measured across the second coil is -3.60 V. What is the mutual inductance of the coils?

So, the equation I have used is: emf2 = -M dI1/dt ...which is the voltage of the second coil equals the mutual inductance times the current with respect to time. I solved for M, but the answer is not right.

My answer was: 80 V*s/A and I got various other answers but they are incorrect.

I really, really would appreciate any help! Thankyou so much!!

#### OlderDan

Homework Helper
edlin said:
Hi..I am new here and I am really thankful for any help that I may get I am stuck in a problem of mutual inductance. It seems fairly simple, yet I cannot get the correct answer.

Two coils are close to each other. The first coil carries a time-varying current given by I(t) = (4.60 A) e-0.0250tsin(377 t). At t = 0.800 s, the voltage measured across the second coil is -3.60 V. What is the mutual inductance of the coils?

So, the equation I have used is: emf2 = -M dI1/dt ...which is the voltage of the second coil equals the mutual inductance times the current with respect to time. I solved for M, but the answer is not right.

My answer was: 80 V*s/A and I got various other answers but they are incorrect.

I really, really would appreciate any help! Thankyou so much!!
Is it by any chance more like 472 V*s/A?.

#### edlin

Well, I actually did get answers in the hundreds, but when I put my answer in, it tells me it has the wrong magnitude. And since they provide me with the units, it says mHz...so the answer is multiplied by 1/10^3.... and I really don't understand why. I get no answer near that.

#### OlderDan

Homework Helper
edlin said:
Well, I actually did get answers in the hundreds, but when I put my answer in, it tells me it has the wrong magnitude. And since they provide me with the units, it says mHz...so the answer is multiplied by 1/10^3.... and I really don't understand why. I get no answer near that.
Are you sure it is mHz and not just mH? The units of inductance are named after Joseph Henry.

H = V·s/A

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