Electromagnetic Induction

Last experiment we discussed about electric currents creating magnetic fields, now, it is the otherwise. This is explained by:

This states that a change in magnetic flux creates an opposing (denoted by the negative sign, which is described by Lenz's Law) induced current. On the other hand, Lenz's Law states that the direction of any magnetic induction effect is such as to oppose the cause producing it. When the magnetic field increases, the induced current is clockwise, when the magnetic field increases, the induced current is counterclockwise.

Before the experiment, we were taught how to use a galvanometer. Its deflection tells the magnitude of the current induced and its direction. We tested it by connecting it to a power supply, and attached a resistor with large resistance. In this case, we used the human body as the resistor, which was quite amazing to know.

In this experiment, we observed the electromagnetic induction in a solenoid in three different ways:

The figure above shows induction experiments due to (A) a moving magnet (B) varying current (C) decreasing number of turns of the primary solenoid

I noticed that the deflection and magnitude readings of the galvanometer are affected by the following:

• the speed of the magnet going in and out of the solenoid and when it stops, the meter reads zero
• the reversing the polarity of the magnet also reverse the deflection of the galvanometer.
• the distance of the primary solenoid from the secondary solenoid
• turning the power supply on and off

It was a simple experiment and everything was straightforward.