Magnitude of induced current

1. Sep 22, 2014

aredy29

A simple experiment of pushing magnet bar into solenoid & pulling it out from solenoid. If galvanometer is used to measure magnitude of induced current, galvanometer will show greater deflection when the bar magnet is pushed into the solenoid but the deflection will be less when the magnet is pull out from the solenoid. Assume force used is equal in both situation. Is there any specific reason for this difference? Does it has something to do with the rate of cutting of the magnetic flux?

I hope someone can answer this because I tried to look for the answer in the web but couldn't find it.

2. Sep 23, 2014

Redbelly98

Staff Emeritus
If the bar magnet is pushed in and then pulled out at the same speed, the rate of change of magnetic flux will be the same (in magnitude), so the induced current should be the same for both cases.

Put another way, if the current are different, then the magnet went in and out at different speeds.

Did you read somewhere that the currents would be different, or is this your own observation from doing the experiment yourself?

3. Sep 23, 2014

aredy29

Thanks for the response Redbelly98. I got it from an exam question. The question said the same force is used to push into & pull out the bar magnet. From that statement I assume the speed of the bar magnet is the same in both situation. The problem is the marking scheme for that question said that the magnitude will be different, induced current when pushing into is greater than when pulling out. I suspected the answer provided is wrong. Do you think the same?

4. Sep 23, 2014

Redbelly98

Staff Emeritus
Hmm, so the wording of the question said there were equal forces, not (necessarily) equal speeds.

Either the two situations have equal speeds, and the answer is wrong, OR the question author had in mind some reason why the speeds would be different -- but I don't know what that thinking would be.