Randolph College

Physics 106 Lab

Magnetism due to a straight wire.

Part 1

Equipment

· D-cell battery in holder

· Wire (probably 2 feet – clip together two or three wires)

· Compass

Purpose of lab:  To measure direction of magnetic field due to current in a wire.

Important safety note: In this lab, you will be connecting the two ends of a battery to each other with a single wire and no load. If the wire is left connected for long periods of time, the battery will become extremely hot, as will the wire. For your safety, wear safety goggles in this experiment and do not have the wire connected for more than 15 second intervals.

Procedure:

Make 3 data sheets for your compass: For each one, cut a square piece of paper 10 cm by 10 cm. Draw lines to indicate 0 degrees, 30 degrees, 60 degrees, 90 degrees, 120 degrees, 150 degrees, 180 degrees, 210 degrees, 240 degrees, 270 degrees and 300 degrees on each paper (see Figure 1).  Label them "with current, one wire" ,"with current, two wires" and "without current".

Do three experiments
Experiment 1: No current

1. Without any wires hooked to the battery, place the paper on a platform that will support the compass and allow you to write on the data as well. (A small piece of cardboard or plastic would suffice) (See video for an idea)

2. Define a circle with a radius about 1/2 the diameter of the compass away from the center.  Measure the direction that the compass needle points for each angle.  Draw little vectors that start from the center of the compass at each angle and point in the direction that the North needle points in. (See video for example).

3.    Take a picture of your data sets for upload to moodle.

Experiment 2: current, one wire (see Figure 2)

1. Now figure out how to wire up your platform so that the wire will go straight through the center (see video on moodle for an idea).

2.     Take the measurements again for each angle.  Take two or three measurements at a time and then disconnect the wire and let the system cool for 60 seconds.

3.    Take a picture of your data sets for upload to moodle.

        Experiment 2: current, two wires (see Figure 3)

1. Now figure out how to wire up your platform so that the wire will go straight through the center and then back down through the hole.

2.     Take the measurements again for each angle.  Take two or three measurements at a time and then disconnect the wire and let the system cool for 60 seconds.

3.    Take a  picture of your data sets for upload to moodle.

Figure 1 Data sheet set-up

Figure 2 Set-up for one wire experiment


Figure 3 Set-up for two wire experiment

Answer informal lab quiz questions on Moodle.

Part 2

Watch this video

Can you explain why the magnets take much less time to fall through the copper tube than if the magnets are outside of the copper tube.