Question

Magnetic induction lab: 5 questions

A vertical bar magnet is dropped through the center of a horizontal loop of wire, with its south pole leading. At the moment just before the south pole passes through the loop, what is the direction of the induced current in the loop (viewed from above)? 2. Explain your answer to the previous question. 3. A vertical bar magnet is dropped through the center of a horizontal loop of wire, with its south pole leading. At the moment when the midpoint of the magnet passes through the loop, what is the direction of the induced current in the loop (viewed from above)? 4. Explain your answer to the previous question. 5. One of the excursions last week involved a long wire passing through the field of a large permanent magnet. If, standing in front of the apparatus, you have connected the power supply such that the current flows from left to right, and the wire is pushed toward you, which of the poles of the magnet (top or bottom) is the north pole? Justify your answer.

Answer 1

1. The direction of the induced current as viewed from above is clockwise
2.The approach of the magnets south pole increases the magnetic flux through the loop and thereby induces a current in the coil.The loop then acts as a magnetic dipole in such a to oppose the increase of the magnetic flux.The direction of the magnetic flux is from south to north
Since the south pole of the magnet is approaching, the coil will have south pole on its face so that it can oppose the magnetic flux
Inorder to have south pole on its face the current should be clockwise .
To get the direction we can use the right hand .We know the direction of the magnetic dipole moment (which is from south to north ) .curl your hand around the coil such that the extended thumb represent the direction of the dipole moment
3.Counter clockwise
4.In this case the south pole is moving away from the face of the coil.Or the field is decreasing in the downward direction .The current will be generated in such a way that it will oppose the change (decrese)
The magnetic field generated on the front face of the coil will be north .So the current direction will be counter clockwise
5. The top part will be north pole