# Magnetic circuit question

• Engineering
the question is;

if there only a current in coil a, and it is AC, calculate the rms current required in coil a to maintain an alternating flux in core section a with a peak value of 1.2T calculate the rm voltages at the two coil terminals if coil resistances are neglected

(attached in the previous question which is continued on by this)

So I derived the magnetic equivalent of this circuit which is basically mmf connected to reluctance (R) equivalent. What do I do from here?

at the moment I am here;

F = R * Flux

With that

F= NI, N = 200, R = Req which i have found already and flux = B*A

200 I = Req * B*A

do i substitute in 1.2T for b and solve for I? then multiple by √2 or am i going in the complete wrong direction?

help will be greatly appreciated.

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rude man
Homework Helper
Gold Member
Did they give you the permeability?

relative permeability is 10,000,
multiply that by uo

rude man
Homework Helper
Gold Member
the question is;

if there only a current in coil a, and it is AC, calculate the rms current required in coil a to maintain an alternating flux in core section a with a peak value of 1.2T calculate the rm voltages at the two coil terminals if coil resistances are neglected

(attached in the previous question which is continued on by this)

So I derived the magnetic equivalent of this circuit which is basically mmf connected to reluctance (R) equivalent. What do I do from here?

at the moment I am here;

F = R * Flux

With that

F= NI, N = 200, R = Req which i have found already and flux = B*A

200 I = Req * B*A

do i substitute in 1.2T for b and solve for I? then multiple by √2 or am i going in the complete wrong direction?

help will be greatly appreciated.

the question is;

F= NI, N = 200, R = Req which i have found already and flux = B*A

200 I = Req * B*A

do i substitute in 1.2T for b and solve for I? then multiple by √2 or am i going in the complete wrong direction?

help will be greatly appreciated.

Well, you got NI = flux*reluctance right, so what's preventing you from solving for I? And yes, you need to divide by √2 to get rms current. The formula NI = R*flux is for instantaneous values of I and flux.

To get the two winding voltages you go to Mr. Faraday.

(Realize that there are two reluctance paths, right?)