Question

Connect the provided coil to the scope and connect the probe one one side and the scope’s ground to the other side. Move the magnet in and out and observe how many volts of EMF you can you produce with the provided magnet and how can you maximize this value. What difference does the orientation of the magnet make? How’s conservation of energy ensured here (discussion)?

the expermental data that have:

south in "+" voltage

north in "-" voltage

+ max =0.225 volts

-max = 0.225 volts

thanks for help

Answer 1

Effect of orientation of magnet

If south pole of the magnet is moved towards the coil, then an induced emf is produced in the coil due to which an induced current will flow and direction of induced current will be such that it may oppose the cause responsible for its production in accordance with the Lenz's law. The end facing the magnet will acquire south polarity due to the induced current so that it may oppose the movement of magnet towards it. It will produce "+" voltage.

When south pole is moved away, induced current will oppose the away movement of magnet as well by acquiring north polarity because it also produces induced emf by decreasing the flux linked with the coil. It will produce "-" voltage.

Similar effects will be seen when north pole is moved towards or away from the coil. But when north pole is moved towards the coil, the end of the coil facing the magnet will acquire north polarity and hence "-" induced volatage will be produced. When north pole is moved away from the coil "+" volltage will be produced.

Energy Conservation

When say north pole is moved towards the coil, the end facing the coil acquire north polarity to repel the magnet. Therefore to move the magnet towards the coil we have to do external work which is converted into electrical energy, hence electrical energy is produced at the cost of mechanical work done against this repulsion. Similarly when we move north pole away from magnet we have to do work against attraction. Hence energy is conserved in this process.

If it is not so, say while moving the north pole towards the coil the end facing the coil acquire south polarity, then it will start attracting the magnet and magnet will gain in kinetic energy even if we stop pushing the maget towards the coil and at the same time electrical energy will be produced. so kinetic energy and electrical energies will be produced at the cost of nothing which is against the principle of conservation of energy.