When do you use N (turns of wire) in Faraday's law and calculating Magnetic Flux

[Brytz]

As the title says, I was doing various questions about DC motors and calculating the magnetic Flux when the coil is perpendicular to the magnetic field. The number of turns in of wire was given to be 50. Would you use phi=BA or phi=BAn in this instance? Also, the question stated, if the EMF is 40mV after a 90 degree turn of the wire, calculate the time taken for the coil to turn 90 degrees. Would you include n in this case or not?

Overall, why do you use n or not for these situations?

[lzxnl]

Think about it. No matter how many coils of wire you have, the area that the magnetic field passes through is the same.
What is the point of the number of coils? Faraday's law of induction applies to each individual coil. If each individual coil induces an EMF of , then summing over all n coils yields

That is where you need the "n". Similarly, for magnetic forces, there is a force on each wire in the same direction. So what happens? You tell me.

[Brytz]

From what I understand. Each coil of wire induces an EMF individually. So that is why the N is part of Faraday's law to find the total amount of EMF induced by the wires. But, what about if you are given a certain EMF and have to calculate the change in time. Would you need N still. Regarding Force, F=nIlB, so, each coil of wire is creating a stronger force.

[lzxnl]

From what I understand. Each coil of wire induces an EMF individually. So that is why the N is part of Faraday's law to find the total amount of EMF induced by the wires. But, what about if you are given a certain EMF and have to calculate the change in time. Would you need N still. Regarding Force, F=nIlB, so, each coil of wire is creating a stronger force.

The first part is correct. Each coil of wire has an identical current moving in the same direction.
If you're given a certain EMF, this is the total EMF induced by ALL of the coils, so you would have to use the number of coils in your response.

It's more that F = iLB on one coil. The force per coil is the same, but add another coil and there is a force on that coil as well. Add a third coil and you have a third equal force, so for n coils, that's where F = niLB.

[Brytz]

Thanks for that. The textbook doesn't really explain when to use N. It makes sense now that each coil of wire is treated separately.