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Calculate the back e.m.f of a 10H, 200 O...

Calculate the back `e.m.f` of a `10H`, `200 Omega` coil `100 ms` after a `100V` d.c supply is connected to it.

Text Solution

Verified by Experts

The value of current at 100ms after the switch is closed is
`I-I_0[1-e^((-t)/(T_0))]`, Here,`I_0=(100)/(200)=0.5` amp,
`tau_0=L/R=(10)/(200)=0.05sec,t=0.1sec`
`I=0.5 (1-e^(-0.1//0.05))=0.5(1-e^(-2))=0.4325A`
Now, `E=IR+L(dI)/(dt),or `
`100=0.4325xx200+L(dI)/(dt)`
Back e.m.f `=L(dI)/(dt)=100-0.4325xx200=13.5 V`
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