#1

Hope everyone is having a grand Sunday morning!

This is just a quickie to see if anyone can help me with a Physics investigation and a bit of theory:

I was investigating how the number of turns of wire that are on an iron core effect the emf seen in the secondary coil when a fixed number are in the primary. Everything went to plan and I think that I got a good set of results, but I'm interested in how power relates to an electromagnet/transformer

I took both Current and Voltage readings so I can calculate it and my graphs of Power vs No. of turns shows a constant relationship, but why exactly does it behave in this way? If anyone can point out the reason, I'd be most grateful

This is just a quickie to see if anyone can help me with a Physics investigation and a bit of theory:

I was investigating how the number of turns of wire that are on an iron core effect the emf seen in the secondary coil when a fixed number are in the primary. Everything went to plan and I think that I got a good set of results, but I'm interested in how power relates to an electromagnet/transformer

I took both Current and Voltage readings so I can calculate it and my graphs of Power vs No. of turns shows a constant relationship, but why exactly does it behave in this way? If anyone can point out the reason, I'd be most grateful

#2

i could have told you abour 6 months ago, i forget now GODDAMMIT!

#3

I thought that conclusion was derivable from the formulas. I think that if you take a glance at them you'll see why.

#4

Well, as far as i know, voltage times current is always the same no matter how many turns are there. Theoretically. In practice, I think that bigger voltage and smaller current give more power as there's less loss due to wire heating and so on.

The reason why power stays the same can be explained in two ways. First - you can't expect to have more (or less) energy in the second than in the first coil...energy cannot be created or destroyed, it can only be transformed. So if the coils aren't heating and losing energy that way, they are equal on both sides. same goes for power, as it is happening in the same time...

Second - voltage grows as the number of turns grow, and current drops as the number of coils grow. So No matter how many turns are there, voltage times current is always the same and that just happens to be the power...

The reason why power stays the same can be explained in two ways. First - you can't expect to have more (or less) energy in the second than in the first coil...energy cannot be created or destroyed, it can only be transformed. So if the coils aren't heating and losing energy that way, they are equal on both sides. same goes for power, as it is happening in the same time...

Second - voltage grows as the number of turns grow, and current drops as the number of coils grow. So No matter how many turns are there, voltage times current is always the same and that just happens to be the power...

#5

Excellent stuff guys, thank you

#6

im sory

WHAAT?

WHAAT?

#7

Aye that point on energy conservation seems sound enough. I think the transformer works because in the first coil there is an alternating current. This generates an magnetic field that fluctuates back and forth. The iron core is a magnetic material and so the fluctuating magnetic field is seen in this core. The other coil of wire is wrapped around this core and the magnetic field induces an alternating current in the second coil because it is moving back and forth. The current induced here depends on the amount of turns the second coil has and therefore the exposure of the coil to the fluctuating magnetic field. Since Power = Energy/Time and also Current x Voltage and energy must be conserved, if a large current is induced in the second coil there will be a small voltage and vice versa.

That's pulling stuff up from a few years ago but I think that's the jist.

That's pulling stuff up from a few years ago but I think that's the jist.