Magnitude of induced current

[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.

 

[Redbelly98]

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?

 

[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?

 

[Redbelly98]

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.

 

[sardar]

The difference in the magnitude of induced current between pushing and pulling the magnet bar into and out of the solenoid is due to the concept of Faraday's Law of Induction. This law states that a changing magnetic field will induce an electric current in a conductor. In this experiment, the magnetic field within the solenoid is changing as the magnet bar is pushed in and pulled out, causing an induced current in the solenoid.

When the magnet bar is pushed into the solenoid, the magnetic field within the solenoid is increasing, which results in a larger change in the magnetic field and a stronger induced current. This is why the galvanometer shows a greater deflection in this situation.

On the other hand, when the magnet bar is pulled out of the solenoid, the magnetic field within the solenoid is decreasing, resulting in a smaller change in the magnetic field and a weaker induced current. This is why the galvanometer shows a smaller deflection when the magnet is pulled out.

Therefore, the difference in the magnitude of induced current is indeed related to the rate of cutting of the magnetic flux. The faster the change in the magnetic field, the stronger the induced current will be. This concept is also known as the law of electromagnetic induction and is crucial in understanding many phenomena and devices in electromagnetism.