# Effect of current induced by rod magnet

1. Aug 25, 2011

### Lesnick

If you had a lined retangular section solenoid inclined at a angle of 45 deg and you rolled a rod magnet ( just fits inside the retagular section) down it. Would the current induced in the solenoid brake or accelerate the rod magnet.

2. Aug 25, 2011

### Staff: Mentor

Welcome to the PF.

I'm not sure that I understand the geometry that you are describing. Also, what is the solenoid wiring connected to? Is there a load resistor, is it shorted end-to-end, or is it open circuit? Could you maybe post a sketch/drawing? I'm assuming the bar magnet has N at one end and S at the other end, right?

3. Aug 27, 2011

### hassanjaved

yep the question isn't clear..

4. Aug 27, 2011

### Bob S

There are several things going on here. The final answer is: no braking and no acceleration.

Assume a solenoid wound around a non-conducting rectangular form sloped at 45 degrees. A long magnetized rod magnetized end to end pulled or pushed through the solenoid will induce voltage pulses in the coil. If the ends of the solenoid are connected to a load, there will be a retarding force due to induced current. However, if a short rod magnetized end to end and rolling down the solenoid, will not induce a voltage, nor any retarding force. This is because both magnetized ends are at the same axial position of the solenoid at any instant in time.

Bob S