What does a motor do?

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Figure 1. An electric motor from an old vacuum cleaner.

An electric motor is a device used to convert electricity into mechanical energy—opposite to an electric generator. They operate using principles of electromagnetism, which shows that a force is applied when an electric current is present in a magnetic field. This force creates a torque on a loop of wire present in the magnetic field, which causes the motor to spin and perform useful work. Motors are used in a wide range of applications, such as fans, power tools, appliances, electric vehicles, and hybrid cars.

How they work

Motors have many different working parts in order for them to continually rotate, providing power as needed. Motors can run off of direct current (DC) or alternating current (AC), and both have their benefits and drawbacks. For the purpose of this article a DC motor will be analyzed, to read about AC motors, click here.

The main parts of a DC motor include:[3]

• Stator: The stationary part of the motor, specifically the magnet. Electromagnets are often used in order to provide more power.

• Rotor: The coil that is mounted on an axle and spins at high speeds, providing rotational mechanical energy to the system.

• Commutator: This component is key in DC motors, and can be seen in Figure 3 and 4. Without it, the rotor would not be able to spin continuously due to opposing forces created by the changing current. The commutator allows the rotor to spin by reversing the current each time the coil does a half turn.

• Power source: Supplies an electromotive force which causes current to flow in the system.

• Brushes: These are connected to the terminals of the power source, allowing electric power to flow into the commutator.

• DC Motor

• Figure 3: A basic setup of a DC motor.[3]

• Figure 4: An animation of the motor in action. The commutator rotates in order for the rotor to spin continuously.[3]

References

"" You might be surprised to find out just how much work is done by electric motors.

HowStuffWorks

To understand how an electric motor works, the key is to understand how the electromagnet works. (See How Electromagnets Work for complete details.)

An electromagnet is the basis of an electric motor. Say that you created a simple electromagnet by wrapping 100 loops of wire around a nail and connecting it to a battery. The nail would become a magnet and have a north and south pole while the battery is connected.

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Now say that you take your nail electromagnet, run an axle through the middle of it and suspend it in the middle of a horseshoe magnet as shown in the illustration. If you were to attach a battery to the electromagnet so that the north end of the nail appeared as shown, the basic law of magnetism tells you what would happen: The north end of the electromagnet would be repelled from the north end of the horseshoe magnet and attracted to the south end of the horseshoe magnet. The south end of the electromagnet would be repelled in a similar way. The nail would move half a turn and then stop in the position shown.

You flip the magnetic field by changing the direction of the electrons.

HowStuffWorks

The key to an electric motor is to go one step further so that, at the moment that this half turn of motion completes, the field of the electromagnet flips. You flip the magnetic field by changing the direction of the electrons flowing in the wire, which means flipping the battery over. The flip causes the electromagnet to complete another half turn of motion. If the field of the electromagnet were flipped at precisely the right moment at the end of each half turn of motion, the electric motor would spin freely.

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