The Electromagnet When you have completed this exercise, you will be able to explain the operation of an electromagnet by using a coil of wire. You will verify your results with a compass and an iron nail. passes through it. When you grasp the conductor with your left hand so that your thumb points in the direction of current 44 Festo Didactic 91580 P0
This conductor is formed into a loop. What directions are shown for the lines of force with respect to the conductor? a. random b. all are in the same direction stronger, or more concentrated, there. Y Festo Didactic 91580 P0 45
turns of the coil. It is also inversely proportional to the length of the coil. You can see this relationship in the following formula. H N = I L N = number of turns of wire I = current in amperes L = length of coil in meters meter. of the equation remain constant)? a. applied current (I) b. number of turns (N) c. length of the coil (L) 500 ma? a. b. c. Just like the permanent magnet, the electromagnet has a north and a south pole, and it attracts only objects made of iron or that have an iron content. 46 Festo Didactic 91580 P0
You can use the left-hand rule to determine the poles of an electromagnet. in which the wire is wound around the coil. circuit board. Locate the plunger (iron bar with hole) and insert it into the coil as shown. Festo Didactic 91580 P0 47
Adjust the positive variable supply to 10 Vdc. Hold the compass several inches to the right end of the coil. Is the compass needle attracted to the coil? a. yes b. no Is the compass needle now attracted to the coil? a. yes b. no Which pole of the compass needle is attracted to the right end of the coil? a. north b. south Hold the compass several inches to the left end of the coil, and press S1. 48 Festo Didactic 91580 P0
Which pole of the compass needle is attracted to the left end of the coil? a. north b. south coil? a. A b. B What property does the electromagnet have in common with the permanent magnet? a. b. one north pole and one south pole c. Remove the plunger (iron bar) from the coil. Adjust the positive variable power supply to 5 Vdc. Locate the iron nail, and hold it loosely about halfway inside the right end of the coil. Press S1. What kind of force can you feel acting on the nail? a. attractive b. repulsive c. none Adjust the positive variable supply to 10 Vdc. Festo Didactic 91580 P0 49
Hold the nail loosely in the same position, and press S1. How does the attractive force at 10 Vdc compare to the force at 5 Vdc? a. The force at 10 Vdc is greater. b. The force at 5 Vdc is greater. c. Both forces are about the same. the applied current? a. directly proportional b. inversely proportional You determined that the force was weak at 5 Vdc but strong at 10 Vdc. An electromagnet has one north pole and one south pole. 1. What can you demonstrate by inserting an iron nail into an energized coil? a. b. c. attractive and repulsive forces d. All of the above 50 Festo Didactic 91580 P0
2. a. reverse the direction of the applied current. b. increase the applied current. c. decrease the applied current. d. reduce the number of turns. 3. board. Set the positive variable supply to 10 Vdc. Locate one of the bar magnets, and slowly insert one end partially into the coil while pressing S1. Notice the type of force acting on the bar magnet. While keeping S1 pressed, reverse the bar magnet and insert the opposite end into the coil. You can feel that one end of the bar magnet is attracted by the coil and the other end is repelled. Festo Didactic 91580 P0 51
What principle have you demonstrated? a. b. c. d. An electromagnet has one north pole and one south pole. 4. What can you use to determine the north and south poles of an electromagnet? a. a compass b. a bar magnet with north and south poles marked c. the left-hand rule d. All of the above 5. What item is not necessary to make an electromagnet? a. an iron core b. a conductor c. a current source d. All of the above 52 Festo Didactic 91580 P0