# Using air core solenoids in a lab exercise

• nmsurobert

#### nmsurobert

I found a box of air core solenoids and was hoping someone could me think of a useful lab to use them for. They are about 700 turns each. They carry 7 to 10 amps. However I think I think I would only be able to provide 3 amps because of the power supplies I have. I would like to use them to do some actually calculations instead of just demo type things.
Any suggestions are welcome. Thank you!

Do you have signal generators and oscilloscopes? Do you know the approximate inductance values of the solenoids? Do you have any ferrous rods that would fit inside of the air core solenoids?

hutchphd

Do you have signal generators and oscilloscopes? Do you know the approximate inductance values of the solenoids? Do you have any ferrous rods that would fit inside of the air core solenoids?
I have non of those things. I might be able to find some iron rods though.
Most 11th and 12th grade. AP Physics 2.

Do you have a way to measure the magnetic field strength at various points?

berkeman
Do you have a way to measure the magnetic field strength at various points?
Oh, good idea. The students could use a compass to map out the external B-field lines and sketch them...

Oh, good idea. The students could use a compass to map out the external B-field lines and sketch them...
I have a bunch of compasses. I guess I'll end up using them. I like qualitative labs, but these students are very bright and I like challenging them a little bit. However, I'm always short on supplies.
You could check out @kuruman's insight. Maybe it'll give you some ideas.

https://www.physicsforums.com/insights/how-to-model-a-magnet-falling-through-a-solenoid/

Qualitative labs can be good too. Have students predict the general shape of the emf induced when they drop a magnet through the solenoid. What happens if they drop the magnet in the other side? Does the curve flip over? Does it stay the same? Explain how they figured it out. That sort of thing.
Thank you for that link! I'll read through it and see if I can take anything from it.

Oh, good idea. The students could use a compass to map out the external B-field lines and sketch them...
I was thinking more along the lines of something like the Pasco Magnetic Field Sensor since the OP wanted a quantitative lab exercise.

I suppose the students could use an app like phyphox on their smartphones to measure the field and map it.

I was thinking more along the lines of something like the Pasco Magnetic Field Sensor since the OP wanted a quantitative lab exercise.

I suppose the students could use an app like phyphox on their smartphones to measure the field and map it.
I've never heard of phyphox. It looks really interesting though. Thank you for that.

BillTre
@nmsurobert -- Whatever method you use to have the students map out the DC magnetic field of the coil, be sure to remind them that the Earth's magnetic field is being vectorially summed with the coil's field in their measurements. So their measurements need to subtract out the Earth's magnetic field vector as part of their data processing.