Question

context: 1A: Using the alligator clip wires, attach the coil with more loops to the galvanometer. Look carefully at the direction that the wires are turned. The idea here is that you will be moving the pole of a magnet closer to the coil— increasing the magnetic field strength in the vicinity of the coil, which is one way to increase magnetic flux. Thinking about the orientation of your loops of wire, and using the appropriate right-hand rule(s), decide which direction the current will be created in the wire as you move the north pole of your magnet towards, and into the center of, the coil—and therefore which direction the needle of the galvanometer will move. Draw a diagram below and the direction of the induced current in the wire coil as the magnet is moved as shown.

questions

Experiment 3: Repeat 1a, but this time hold the magnet still and move the coil toward the magnet. How does the created current in this case compare to that in 1a (in magnitude and direction)? Why?

Experiment 4: Repeat 1a but with the S-pole facing toward the loop. Is it any different? How? Why?

Answer 1

1A:

According to Lenz's Law induced EMF due to changing magnetic field near a loop of wire opposes the change of the field.

The coil is on the left, and on its right a magnet is being accelerated towards the loop, from the magnet's perspective the wire in the loop is on clockwise direction.

Now as the field changes near the loop the induced current in the loop will generate a magnetic field towards right. To generate this field, according to the right hand thumb rule, induced current has to flow anticlockwise in the loop.

If this current is going to enter the positive lead of the galvanometer, then the deflection will be towards right, otherwise it would be towards left.

3.

As induced current depends on the changing magnetic field, which depends on the relative speed between the coil and the magnet, so the movement of the coil will be as same as the situation where the magnet moves relative to the coil. So the magnitude of the current and the deflection will be the same.

4.

As the magnetic field is inverted, so will be the current (according to Faraday's law they are proportional), as the current is inverted, the needle in the galvanometer will be deflected in the opposite direction.