# What happens to the current when this solenoid's diameter is doubled?

1. Nov 17, 2008

### selishaphysic

In an induction experiment a tightly wound solenoid is used to produce a current of 2A. The
solenoid is then unwound to make another tightly wound solenoid of twice the diameter.
What current would you expect to get if you use the new solenoid in the same experiment?

I'm new to this forum and I just learned that I'm supposed to show my own effort here or maybe what I understand. Well here it comes (I'm not very good at physics). I've learned in physics class that the induced emf= number of loops times the magnetic field times the change in area over the change in time. I know that the area will be bigger which will make the induced emf bigger, but what about the current, what formula should I use here? Just by thinking about P=IV I get confused since then I would wanna know the power and the voltage. Although now that I think of it more, when the diameter is bigger the number of loops around the solenoid are getting less and the area is getting bigger so it's basically the same. So we get the same current in both. Am I thinking right ?

Last edited: Nov 17, 2008
2. Nov 17, 2008

### LowlyPion

If you double the diameter what happens to the area over which there is magnetic flux?

3. Nov 17, 2008

### selishaphysic

I know that the area will be bigger therefore the flux will be larger, but this doesn't mean that the current will be larger does it? Since the number of loops will be less if the diameter is bigger right? So my conclusion is that the current will be the same since the induced emf is the same. Please tell me if I'm thinking right or wrong.

4. Nov 17, 2008

### LowlyPion

How much bigger is the area if the diameter is doubled?

What are the equations that determine current from flux?