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EGN 100 Introduction to Engineering Magnetic Fields Lab In magnetism, direction is defined by naming one pole of a magnet the north pole and the other the south pole. The magnetic field of the earth was known in early times, in that a magnetite (a mineral, naturally occurring material) needle floating on water would line up in a north-south direction. A compass is a simple tool that can be used to determine the direction of a magnetic field. The compass needle points in the direction of the field. See http://www.howstuffworks.com/compass.htm . Observe carefully and record all observations. Part A With the magnet and compass on the table as shown, explore around the magnet with the center of the compass about 4 centimeters (1.5 inches) away from the magnet. Do not bring the compass close to the magnet. How does the direction of the of the compass needle change as you explore? When done, place the magnet a few feet away so it doesn’t interfere with the next experiment. What conclusions do you draw regarding the direction of the magnetic field around a bar magnet? Part B We will use the power supply as a current supply. Set the voltage of the power supply to 1 volt. Turn the current limit down to as low as it goes. Place the wooden wire support so the wire is horizontal. Connect the end of the wire with a dot on the post to the positive terminal of the power supply. Connect the other end of the wire to the negative terminal. Adjust the current to about 2 amperes. Disconnect the wire from the positive terminal. Consider positive current to come out of the positive terminal. Sketch the apparatus and the direction positive current flows through the wire. Line up the compass and the wire so that the wire is oriented in a north-south direction, with the dotted post in the south direction. The compass should be on or slightly above the wire and midway between the wooden posts. The needle should be pointing in the direction of the wire. Keep the compass horizontal at all times so that the needle can rotate freely. Connect the wire to the positive terminal and record the direction of the compass needle (north, south, east, west, or something in between). Move the compass to a position just below the wire. What is the direction of the needle? What conclusions can you draw regarding the direction of the magnetic field produced by a current flowing through a wire? Part C Turn the board so the wire is vertical. Keeping the compass horizontal and next to the wire, move the compass around the wire. How does the direction of the needle change? Assume that the compass needle is lining up with magnetic field in the space surrounding the magnet or the wire. Sketch the magnetic field direction. Discuss your observations. What conclusions can you draw regarding the magnetic field produced by a current flowing through a wire? Part D On the power supply, set the voltage to 1.0 volts and reduce the current limit to its minimum setting. Connect one end of the wire coiled around the bolt to the negative terminal and the other end to the positive terminal. Increase the current to about 2.0 amperes. Explore the magnetic field around the electromagnet with the compass 4 centimeters (1.5 inches) distant from the electromagnet. Do not bring the compass close to the electromagnet. Record your observations. Keeping the electromagnet in the same position and orientation, reverse the connections of the wires to the power supply. Explore the magnetic field around the electromagnet and record your observations. Compare these observations with those for the first current direction. Disconnect the wires from the power supply. What do you conclude from these observations? Write your conclusions on a piece of paper. Place the compass a few feet away so it will not be affected by the next experiment. Part E Merge two teams so you have two cylindrical magnets. Place one magnet on the table surface with the rolling surface on the table. Holding this first magnet in place, gently bring a circular end of the second magnet toward a circular end of the first. What happens? Bring the other flat end of the second magnet toward the same flat end of the first. What happens? Repeat this procedure, but don’t hold the first magnet in place. What happens? What do you conclude from these observations?