Topic 1: A LAB REPORT ON THE SIMPLE CONSTRUCTION OF AN ELECTRIC MOTOR
There exists an innate relationship between electricity and magnetism and how an electric current interacts with a magnetic field. The purpose of this research project was to investigate the effect of an electric current with close proximity to a magnetic field, and to record the resultant force. The experiment was setup using simple lab equipment. The size of the magnet, amount of current and the number of turns of the loop were altered and the different results recorded.
The results showed that changing the different variables like amount of current and size of the magnet has a direct relationship to the torque created. The functioning of the electric motor is highly dependent on the torque which may be used in propelling electric machines like cranes and fans.
The discovery that reducing the number of loops reduces variable resistance sets up scientific research questions on more effective methods of reducing resistance in order to improve efficiency in the working of a motor.
The validation of the hypothesis will allow for immediate incorporation of the motor in simple machines that are otherwise not able to be used with ease. Compression of this mechanism into small packages like air drones will only serve to increase usability and variation in use.
Keywords: electricity, magnetism, magnetic field, current, electric motor.
- The aim of this experiment is to construct a simple crude working electric motor using readily available laboratory materials.
INTRODUCTION AND BACKGROUND INFORMATION
The electric motor is a revolutionary creation in the field of technology and science which has helped in the growth of the motor and machine industries. Macro-processors and micro-processors have also changed from using very inefficient, poor systems and are now using improved modern technologies.
More than 85% of the total rotor products produced in the world are modeled on the basic principle of the motor. Motors have become so essential that more than 700 million motors in differing sizes and functionality have been developed to increase precision and significantly reduce cost.
An electric motor works in the presence of a magnetic field. There are two major parts which are the rotor and the stator. Any of the two components produces the necessary motion power; hence called the armature.
The rotor/armature is made of a coiling electrical wire around the magnet. The stator is then the magnet which produces the magnetic field that interacts with the rotor for motion to be created. The coiled wire then experiences an amount of force that causes the motor to work.
- A coiled electric wire with an electric current around a magnet experiences a torque/force due to the magnetic field around the magnet.
MATERIALS AND METHODOLOGY
- Power supply (30 V emf with 1 A of current)
- Wood block baseboard with magnet pedestal and bearing posts (5*7 in.).
- Neodymium disk magnets (847-647-0011; product # 10584).
- Enameled wire (either 22 or 24 American Wire Gauge); [(561) 848-8236 product # 7255 WI].
- Clip leads
- Long-nose pliers
- Razor knife
DESCRIPTION OF EQUIPMENT
Use a 30 V of electromotive force (emf) and an electric current of 1A. you can use a battery, cells or a small generator able to regulate flow of current.
The enameled wire is design specifically to be used as a coiling wire in magnets, thus called a magnet wire. The diameter, circumference and insulation of the wire should be thin (minimal) in order to allow for continuous looping (too close loops increase resistance!). In this experiment, two types of wires were used: the AWG 22 with a diameter of 0.644 mm, resistance of 16.5 Ω (ohms) and a density of 1.94 lb and the AWG 24 wire with a diameter of 0.511 mm, a resistance of 26.2 Ω and a density of 1.2 lb.
Loop the copper wire in a continuous round loop around a cylindrical, circular or spherical object (e.g. a film canister, battery cells or around the thumb), depending on the number of turns you need. The number of turns should at least be in tens, that is, above 10 loops. Slowly pull the wound section of the wire off the object and gently extend a small piece of the wire horizontally on both sides, about 1 inch.
Small pieces of the copper wire can be used to hold the loop together. The higher the number of turns used, the more the torque that will be created. However, increasing the number of turns increases resistance and the resulting moment of inertia. The armature should be as shown in Fig. 1 below.
Use the motor base to fasten and suspend the armature. The two endings of the copper wire should be fastened to the two opposite metal posts. The two holes allow for easy and unstrained rotation within the base. The final set-up should be as in fig.2.
Use the sandpaper or the razor knife provided to gently scrape off the insulation on the copper wire on one end of the armature. This is to facilitate flow of current through the wire to create a continuous current when the force is in the proper direction. The flow of current thus flows in one direction, for example, the clockwise direction and only supports the rotation of the rotor halfway (1800). Clipping of the copper wire on one side prevents opposing forces of a clockwise and counter clockwise movement from counter-action which causes the motor to only move in half turns. The complete rotation is achieved by inertia.
Push/nudge the motor forward with gentle force to provide initial power for its rotation and the rotor will start moving round (clockwise direction). If rotation does not happen, possible reasons could be: a) stripping of the rotor was done incorrectly, b) the circuit is incomplete, c) the rotor is not at the same height with supporting clips, d) the rotor may not be near enough to the magnet to be affected by its torque or the source of power does not give enough electric current (check using a voltmeter).
It has been noted that altering different components of the motor setup gives differing results in terms of speed of rotation, resistance created and overall torque. The velocity at which the motor turns around the support base, and consequently the amount of force generated changes due to
- Using a higher or lower number of turns of the wire (loops carrying the electric current).
- Using a battery that has a higher or lower voltage (amount of current).
- Using a thin or thick wire which in turn causes differences in resistance.
- By using more or less number of magnets or alternatively using stronger or less powerful magnets.
- These alterations affect the amount of current that passes through the wires and hence affects the rotation of the motor.
Since resistance cannot be controlled, it is important to factor it in the final calculation of torque in order to obtain an accurate result. Hence, a voltmeter may be used to account for resistance and at the same time to record different values of electric current discharged by the power source.
The results obtained did not, however, factor in the effects of air pressure and/ or humidity that had been experienced in the environment of the setup.
Increasing the amount of current has been noted to increase the speed of the rotor and the general working of the motor itself. However, continuously increasing the amount of electrical energy supplied into the system will have little to no effect on the speed of rotation of the rotor at a given maximum limit as shown in the data and calculations section.
In contrast, changing the power of the magnet by increasing its strength has led to increased efficiency in the working of the motor, and continuous increase in number of magnets shows an increasing trend.
DISCUSSION AND EXPLANATION
An electric motor works on a rather very simple technique. The principle is that an electric wire with a given amount of current will experience an effect in terms of force (torque) when it is placed near or within a region that has a magnetic field. The amount of torque created by the motor (Fating et al. 2008) then forces the motor to spin within the base.
The force thus produced is affected by the size of the electrical charge, the length of the wire (the number of loops/turns) and the power of the magnet. Hence, force is a function of the product of current, length of the wire and the magnetic field.
Force= length of wire * magnetic field * current
The direction that the electric charge flows and that of the magnetic field affects direction of the force hence direction in which the motor rotates. The Right Hand Rule is used which states that “If the right hand is held in such a way that the thumb points towards the direction of the current and the first finger towards the magnetic field, then the middle finger will show the direction of the force/torque.” When the rotor rotates in a clockwise direction, then the torque experienced is negative while an anticlockwise rotation shows a positive force (Bianchi and Bolognani 2002).
The motor setup will result in no external force if the magnetic poles are placed parallel to the direction of the field created by the magnet. Additionally, many turns of the wire will increase resistance and thus reduce the electric current acting on the motor.
This demonstrates an inverse relationship between number of loops and amount of torque. Thus, great care should be taken when using the results in a practical situation to account for the effect of resistance.
The advantage of the working of a motor is that changing the direction of the magnetic field or the direction of current will consequently change the direction of rotation. This means that the motor can be used in machines that require movement in both directions, alternating. Moreover, the electric motor can be used as both an AC motor and a DC motor based on motion of current, and the source of power can be in parallel or series (giving differing strengths of current).
Electric motors have become a cornerstone in many industries when it comes to overall practicability. The principle in motors has been used in many emerging technological equipment like in operation of cranes and winches, electric vehicles, solar plane, air compression and water pumps, carnival rides and space stations. Due to the various components involved in the working of the motor and their sequential effects in terms of resultant force, then the practical applicability of the motor is extensive.
When an electric current flows through a cable wire, it experiences some opposing force as a result of friction. An accumulation of this frictional force usually causes loss of electrical charges as the current flows through. Over long distances, resistance may accumulate enough to hinder continuous flow of electric currents. Hence, the effect of resistance resulting from the loops greatly hinders the working of the electric motor and is therefore disadvantageous.
Hence, extensive research needs to be done in this field in order to be able to regulate or control the negative influence of resistance. Eliminating or minimizing resultant resistance will open up the functionality of motors in other industries such as aircrafts and oil rigs. Nevertheless, the motor is a revolutionary tool in the contemporary and scientific world and further research should be done for increased usability.
Nicola, B. and Silverio, B. (2002). Design techniques for reducing the cogging torque in surface-mounted PM motors. IEEE Transactions on Industry Applications. Vol.38, Iss. 5. Pgs (1259-1265).
Fating, V., Jadhav, S., Ugale, T. and Chaudhari, N. (2008). Direct torque control of symmetrical and asymmetrical single phase induction motor. Power System Technology and IEEE Power India Conference, 2008. Pgs (1-4).