i need help with a school project. im in high school.
I follow Big's logic, but I don't agree...for several reasons 1..every motor is operating in a magnetic field right now...earths'. 2. every motor in a plant--power plant, production line, whatever--is operating right now in the additional magnetic field of the motors next to them in the plant. 3. A constant magnetic field might 'twist' the produced field in the motor, but shouldn't have a big effect on the motor itself. Now, a _changing_ magnetic field , a strong one, in the area of the motor might have an effect. This by itself is an interesting question that would make a good project, and it's something that is testable.
Yes. a magnetic field definitely affects an electric motor. That coil of wire in the middle of an electric motor is charge and becomes an electromagnet when it is powered on. On the outside casing there are magnets as well. For every 1/2 revolution of the motor (DC motor), the polarity of the electomagnet is switch so that the polarity of the electromagnet is always the same as the magnets on the external casing. This causes the magnets to always repel each other and is what keeps the motor spinning. The mechanism by which the polarity switches is a bit different in an AC motor, but the overall principle is still the same.
Yes and no. Yes, the theory of magnetic interference is true. However, the electrical coil serves as magnetic shielding, so the penetration of the interfering field is minimal. The global field of the earth is very minimal. As far as magnetic interference from other motors in the area, this is more valid than the global interference argument, but the field generated OUTSIDE of a solenoid coil is very weak compared to that INSIDE the coil. That said, issues can arise if you have forces exerted on the motor or other parts of the drive by a strong field. Strong magnetic fields can generate forces against shafts, gears, and bearings that can be mechanically damaging and cause excessive wear. Typically areas that have strong magnetic radiation are classified, if you've got a deviant field somewhere that is exposed for no good reason, throw up some shielding. OSHA said so. The difference for your AC vs DC motors... A DC motor can potentially be driven by a strong magnetic field (1 in a million odds to get the right induction) an AC couldn't. An unshielded DC motor would possibly exhibit a strong reactoin than an AC motor, but either event is pretty unlikely. Bottom line, if a motor is operating in a strong magnetic field, shield it and you'll have no problems. PS... Simple Mag shielding basically consists of metallic mesh screens. As the mag field penetrates the mesh, essential tries to induce a current and the field is bent around the individual wires, breaking up the field.
An electric motor has a rotating armature, and stationary field magnets. The armature's magnets are usually electromagnets, and the field magnets are usually electromagnets in large motors, or permanent magnets in small motors. Whether it's an AC or DC motor, the rotation comes from the interaction of the armature with the field magnets, either attracting or repelling each other. It takes a very intense magnetic field to produce the forces that rotate the motor, and the magnets within the motor are designed to direct the fields so that they can interact strongly. Magnetic fields' intensity varies inversely with the square of distance from the magnet. That means if you move 2x as far from a magnet the intensity drops to 1/4 and if you move 3x as far from a magnet its intensity drops to 1/9. This means that for the motor to be powerful, its magnets must not only be strong, but very close to each other as well. So, what about an outside magnetic field? Will it affect the motor? Yes, it will, but the real question is - how much? Most magnetic fields in our world are not very strong, and not anywhere near as strong as those found inside a motor. In addition, the source of an outside magnetic field is going to be much farther away from the motor than the motor's magnets are from each other. Finally, most practical motors are enclosed in a metal frame that blocks magnetic fields from getting in or out. As a practical matter, a normal outside magnetic field would be too feeble in comparison with the motor's own fields to affect a normal motor. To have a noticeable interaction would require an exceptionally strong outside field, and a very small motor.
