# When there is change of magnetic flux due to a.c in 1 coil,how induced varying current flows in another coil? diagram

The Faraday induction law for a coil says that the induced voltage is proportional to the rate of magnetic flux variation through the coil taken with changed sign.

`U_("ind") =-(d(Phi))/dt =-(d(B*S))/dt`

The minus sign in front of the above relation means that the induced voltage always opposed the tendency of...

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The Faraday induction law for a coil says that the induced voltage is proportional to the rate of magnetic flux variation through the coil taken with changed sign.

`U_("ind") =-(d(Phi))/dt =-(d(B*S))/dt`

The minus sign in front of the above relation means that the induced voltage always opposed the tendency of variation the flux. Since the induced current is obtained just by closing the circuit, the induced current will have the same behavior, it will tend to oppose the variation of the magnetic flux into the coil.

For example, if both coils are wired the same way (like right wire turns in both), if the current decreases in the first coil, the total flux in the second coil will decrease, and the induced current in the second coil will increase (to generate a self-flux that is opposing the decrease of the flux from the first coil).