Procedure

1. Magnetic Field Map of a Bar Magnet

You will use a small compass to map out magnetic field lines of a permanent bar magnet.

Determine which end of your compass points North. Ask your lab instructor if you are not sure which direction corresponds to North. Make sure the compass is far away from any permanent magnet while you do this. Note: you may wish to check this more than once. The magnetic fields of the bar magnets used in this lab are strong enough to "flip" the poles of the compass needle, as you can observe by gently swiping either pole of the bar magnet quickly across the face of the compass (do not let the magnet touch the glass of the compass if you decide to try this). With a bit of practice, you can reproducibly toggle the magnetic polarization of the compass needle with every swipe.
Once you know which end of your compass needle currently points north, check to see which end of your bar magnet is the North pole end. The compass needle should point away from the north end.
Place your magnet in the center of a piece of paper. Trace the outline of the magnet and label the North and South poles. Using your compass, trace out the shape and direction of at least eight magnetic field lines. Start your lines from a variety of locations on the magnet: begin by marking the tip and tail of the needle, then move the tail where the tip was and mark the tip. Keep doing this until the field line reenters the magnet or leaves the page. Include at least two field lines that stay completely on your page, and show at least two lines that leave each pole end.

2. Verification of Lenz's Law

Study your coil carefully until you have determined how it is wound (ask for help if you are unsure). Orient the coil so its winding is clockwise as you look at it, and then connect it to your galvanometer so that clockwise current leaving the coil flows into the negative (black) terminal of your galvanometer.

Now take a permanent magnet, and quickly push the North end into your coil. You should observe the galvanometer needle to deflect, indicating an induced current.

The galvanometer needle deflects toward the pole that current flows into. Thus, you can detect the direction of current flow by observing the galvanometer needle.

If you have connected your coil and galvanometer correctly, you should observe the following:

To analyze Lenz's law for this situation, follow these steps:

From the galvanometer needle deflection, observe the direction of induced current flow. In this case, current flows counter-clockwise in the coil.
Identify the change in flux. In this case, magnetic flux changes from zero (no magnet) to a non-zero flux caused by field lines piercing into the coil.
Identify how the induced current opposes the change in flow. In this case, counter-clockwise current produces a magnetic field out of the coil, according the right hand rule. Since the magnet movement increases the inward flux, an outward flux is induced to oppose this change.

Analyze all possible cases, and record your observations.