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Measure Your Magnetism

Measure Your Magnetism

The goal of this project is to build a sensor for measuring magnetic field strength and to use it for measuring the strength of different types of magnets.
Magnets and magnetic fields are used in everyday electrical equipment such as motors and refrigerators. You will also find them in electronic equipment like cell phones and radios. A magnetic field can be produced by a permanent magnet, or by electrical current flowing through a wire. You can make an electromagnet by wrapping a coil of wire around a magnetic material (e.g., iron, magnesium, or cobalt). When current flows through the coil, a magnetic field is produced. This type of magnet is an electromagnet.

Magnetic fields are also important in communication systems. The waves used to transfer information for television and radio broadcasts or cell phone calls are electromagnetic waves. Light, x-rays, and radio waves are all examples of electromagnetic waves.

The strength of a magnetic field can be measured. Magnetic field strength is measured in units of gauss (abbreviated G). The device that is used to measure the magnetic field strength is called the gaussmeter.

The gaussmeter that you will build for this project is based on the Hall effect, discovered by Dr. Edwin Hall in 1879. Hall discovered that when a current is passing through a thin sheet and a magnetic field is applied perpendicular to the sheet, a voltage (called the Hall voltage) is generated across the third dimension, perpendicular to the direction of the original current. The magnitude of the Hall voltage is proportional to magnetic field strength. The Hall effect is used in different applications including making an electric motor.

Your gaussmeter will be based on an integrated circuit that allows you to measure the Hall voltage generated by a magnetic field. You’ll learn how to build the gaussmeter, and how to use it to measure magnetic field strength. You’ll also learn how to use your gaussmeter to identify the north and south poles of a magnet.

Materials and Equipment

To do this experiment you will need the following materials and equipment:

digital or analog multimeter,

9 V battery,

9 V battery clip connector (e.g. Radio Shack 270-325),


+5 V voltage regulator (7805 or NTE1934, e.g. Radio Shack 276-1770),

solderless breadboard (e.g., Radio Shack 276-175),

jumper wires for breadboard (e.g., Radio Shack 276-173),

alligator clip leads (e.g., Radio Shack 278-1156),

Hall effect linear IC (A1321EUA),

magnets with different shapes.

If you want to build and measure the strength of simple electromagnets, you will also need:

one or more iron nails,

insulated hook-up wire,

a battery,

wire cutters.

Experimental Procedure

The Experimental Procedure for this project has four sections, which are described briefly below.

Using a Solderless Breadboard. You will be building your gaussmeter on a solderless breadboard. The first section explains how breadboards work.

Building the Gaussmeter. This section has the step-by-step instructions for assembling the gaussmeter circuit.

Measuring Magnetic Fields. This section shows you how to use the gaussmeter to measure magnetic fields.

Analyzing Your Results. This section shows you how to calculate magnetic field strength from your measurements, and also how to identify the north and south poles of a magnet.

Using a Solderless Breadboard

Figure 1, below shows a small solderless breadboard, used for quick assembly of a circuit for testing or experimentation. The breadboard has a series of holes, each containing an electrical contact. Holes in the same column (examples highlighted in yellow and green) are electrically connected. When you insert wires or component leads into holes in the same column, the wires and leads are electrically connected. The two single rows of holes at the top and bottom (highlighted in red and blue) are power buses. All of the red holes are electrically connected and all of the blue holes are electrically connected. Connect the red (+) wire from the battery connector to one power bus, and the black (− or common) wire to the other power bus. Then you can use jumper wires to connect components to the buses.

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