Practical Exercises on Electromagnetism - Assignment Example

Electromagnetism Practical Exercises Name of Student: Student No: Date: Name of Supervisor: The Motor Effect 1. According to Fleming’s Left Hand Rule, the magnetic field will travel from N to S. The coil of wire will turn away from the magnetic field when the current is passed through it in the direction shown. 2. When the current in the coil is reversed, there is a magnetic force at a point in a magnetic field which is always perpendicular to the direction of the current which creates that field as well as the distance vector (r) which defines a point in that field. When the current is reversed, this will cause the direction of the magnetic force to reverse as well at a point that is some distance from the wire. 3. Magnetic field strength = 0.30T Length of one side of the coil inside the magnetic field = 8cm Finding the force when: i. I is 7.2A: Magnetic force (F) = Current (I) * Length of wire (l) * external magnetic field (B) Therefore force = 0.30 *8*7.2 = 17.28 ii. When I is doubled: Force = 0.30*8*(7.2)(2) = 34.56 iii. An extra turn double the length of the wire inside the electric field: Force = 0.3*16*7.2 = 34.56 4. How loudspeakers work. A source of audio produces an electrical signal which manifests as sound. This means that the electrical signal is of the same frequency and content of harmony as well as size which mirrors the relative intensity of sound as it alters. The amplifier takes this electric image and amplifies it, so that it is powerful enough to drive the coils of a loudspeaker. When the amplifier is classified as high fidelity, it implies that this enlargement can take place without change of properties. Any alteration would be viewed as a distortion of sound by the ear which is extremely sensitive to any change. Once the image has been amplified, it is applied to the voice coils of the loudspeaker, causing vibration in a pattern that mimics the changes in the original signal. The voice coil is connected to and moves the cone of the loudspeaker which causes the air to move. This movement of air is the source of the sound pressure variations of the original signal (Institute of Physics, 2013). References Institute of Physics. (2013). How do Speakers Work? Accessed 14 Mar. 13 from: http://www.physics.org/article-questions.asp?id=54 Practical Write-Up Aim The aim of the project was to build an electric motor. Introduction There are certain materials found naturally which have the characteristic of attracting or repelling each other. These materials are known as magnets or ferromagnetic because they are composed of iron as a component of their elements (Zorbas, 1989). Figure 2: Lines of force in a magnetic field. Electricity is the flow of positive or negative charges and it flows through elements known as conductors. It can also flow through clouds of ions in space or in gases. Both these types of conduction are found in electric motors (Say, 1978). Figure 3: The flow of electricity Method Materials Needed Steel rod, 1/8” diameter * 7” long, straight. 8d common nails 2.5” long with flat head. Magnetic wire, 20ft. 35mm film canister round with cover Plywood board 6”*6” piece. Plywood 3”*1”*1/2” pieces Fender washer 1” diameter * 1/8 hole Strong ceramic magnets Stranded hook-up wire 16 in., 12 gauge Alligator clip test leads 4D cell batteries Duct tape Sand paper Mini hot melt glue sticks. Tools Needed Hand saw Drill Wire stripper/cutter with 12 gauge hole. Aviation snips Bolt cutters. Pliers Hammer Small flathead screwdriver Mini hot melt glue gun Ruler Fine point marker. Method Step 1: Armature The two nails are taped together using electrical tape with opposite ends touching. The steel rod is stuck between the nails and the nails are slid to the middle of the rod. The steel rod should be placed exactly at the centre of the nails. The nails are held perpendicular to the rod and glued in place with hot glue. The magnet wire is folded in half and marked at the centre with a piece of tape. The first 12” of the wire is left free and unwrapped. The wire is placed over the top of the nails to the right of the steel rod and wrapped away from you. The wire is wrapped back and forth, while staying on the right side of the nails until the centre of the wire. One more turn is made while crossing the wire to the other side of the nails. The nails were then flipped around and the wire continued to be wrapped. The last 12” of the wire is hanging freely at the end of the coil. The leads are sanded back to the electromagnet. This was then tested. Step 2: Commutator A nail is used to punch holes in the bottom of a film canister, and its lid at the exact centre. The film canister was then slid onto the steel rod until it was about ½ inch away from the electromagnet and hot glued in place. The electromagnet is held straight up and down and a piece of tape along the film canister side is put on. Each lead of the electromagnet is folded back and forth along the length of the film canister. The electromagnetic leads are taped to the top and bottom of the film canister. Step 3: Bearing Blocks Step 4 and 5: making magnetic frame and brushes. Step 6: Assembling the Motor The front bearing block is placed flush against the edge of the motor base so that the washer is about the centre of the base, and hot glued in place. The armature is slid in place and also the back bearing block. The spacing is adjusted until the 2-3” between the electromagnet and the front block so that the motor shaft sticks out of the front block by half to one inch. The magnet frame is placed directly over the electromagnet and hot glued to the base. One magnet is stuck inside the top of the magnet frame and the other magnet is held directly under the electromagnet. The gap between the electromagnet and the magnets is 1/8”. The brushes are placed on the left and right sides of the commutator so that they are touching the masking tape. The brushes are taped to the base with masking tape. Alligator clip test leads are used to connect the brushes to the 4D-cell battery pack. References D. Zorbas. (1989). Electric Machines-Principles, Applications, and Control Schematics. West. M. G. Say. (1978)/. Alternating Current Machines. Pitman Publishing. Read More