Lab 6:Electromagnetic Induction

Purpose/objective:

In this activity you can investigate how a changing magnetic flux can produce a flow of electricity.

Equipment needed:

1. Computer

2. Paper, Pencil

Theory:

A voltage is induced in a coil when there is relative change magnetic field which can be achieved either moving a coil in a stationary magnetic field or moving a magnet around a stationary coil. According to Faraday's Law of Induction, a changing magnetic flux, through a coil induces an EMF given by:

= -N d/dt Eq. (1)

where and the second equality is valid if the magnetic field, B, is constant over the area, A, and perpendicular to the area, N is the number of turns of wire in the coil. For this experiment, the area of the coil is constant and as the magnet passes into or out of the coil, and Equation 1 becomes:

= - NA(dB/dt) Eq. (2)

Lens' Law states that the current induced in a coil by a changing magnetic field through the coil will flow in a direction to oppose the change which produced it. In particular, the field produced by the induced current will be in a direction to try and prevent the field through the coil from changing. Negative sign in equation (1) and equation (2) come from Len's law.

Procedure

1. Go to the following website:

https://phet.colorado.edu/en/simulation/faradays-law

(You can also google for "Faraday's law Phet simulation ".)

You will see first page as shown here.

1. Click to run the program (There is a download option too, you can download it in your computer and open there too.)
2. Try to understand how each icon represents. Move around and be familiar with the simulations

Observations:

1. What happens to the current when the bar magnet is moved up and down?

1. What happens to the current when the bar magnet is moved in and out of the coil?

1. When is induced current direction changes?

1. What happens when you move magnet slow vs fast?

1. As the bar magnet enters the coil from the left, draw (see example) a Right-Hand-Rule to describe the conventional current flow.Remember, thumb always points north.

1. Predict the conventional current flow if you move the bar magnet from left to right ?

a) as the S-pole enters the coil to the left: electrons at front move up or down ?

b) as the N-pole leaves the coil to the left: electrons at front move up or down ?

1. As the bar magnet leaves the coil to the right, draw a right-hand rule to describe the conventional current flow. Remember, thumb always points north.

1. Predict the conventional current flow if you move the bar magnet from right to left: (1 mark)

a) as the S-pole enters the coil to the left: electrons at front move up or down ?

b) as the N-pole leaves the coil to the left: electrons at front move up or down ?

1. Study the effect of no of coils comparing two coils (small vs large coil) on generated current.

a) is there any difference in the induced current magnitude with the similar speeds of the magnet through the small coil vs large coil .

b) is there any difference in the direction of the induced current depending on the size of the coil ?

Conclusions:

Write what you learned from this experiment?