Physics - Electric Motor

Introduction

• An electric motor is a rotating device, which is made to convert electrical energy into mechanical energy.

• We use dozens of devices in which electric motors are used, such as, refrigerators, mixers, fans, washing machines, computers, etc.

• The commercial and high power motors use −

  • An electromagnet in place of a permanent magnet.

  • Large number of turns of the conducting wire in the electric current carrying coil; and

  • A soft iron core on which the coil is properly wound.

• The soft iron core (wound with the coil) and the coils, are known as an armature.

• Armature has main function to enhance the power of the motor.

Electromagnetic Induction

• In 1831, Michael Faraday, an English physicist, had discovered that a moving magnet can be used to generate electric currents.

• As shown in the image given above that the moving magnet towards a coil sets up current in the coil circuit, which is indicated and read by deflection in the galvanometer needle.

• Because of the changing magnetic field, Electromagnetic induction produces an electromotive force (emf) in a conductor.

• A galvanometer is an instrument that is used to detect the presence of a current in a circuit.

Fleming’s Right-Hand Rule

• Fleming’s right-hand rule states that “Stretch the thumb, forefinger and middle finger of right hand so that they are perpendicular to each other (see the image given below). If the forefinger indicates the direction of the magnetic field and the thumb shows the direction of motion of conductor, then the middle finger will show the direction of induced current. This simple rule is called Fleming’s right-hand rule.”

Electric Generator

• An electric generator is a device that converts mechanical energy into electrical energy.

• In an electric generator, mechanical energy is used to rotate the conductor in a magnetic field, as a result of this electricity is produced.

Types of Electric Current

• Following are the two types of electric current −

  • Alternating Current (or AC)

  • Direct Current (of DC)

• The difference between the alternating current and direct current is - the alternating current keeps reversing its direction periodically; whereas, the direct current always flows in one direction.

• Most of the electric power stations produce alternating current.

• In hour houses, there are different electric appliances, most of run on alternating current.

• In our house wiring, fuse is the most important safety device.

• Fuse is used to protect the circuits that may damage due to short-circuiting or overloading of the circuits.