As the armature rotates, a voltage is generated in its coils. In the case of a generator, the emf of rotation is called the Generated emf or Armature emf and is denoted as Er = Eg. In the case of a motor, the emf of rotation is known as Back emf or Counter emf and represented as Er = Eb.
What is DC emf?
A Direct Current (DC) electromagnetic field refers to a constant or static DC electric or DC magnetic field emission which has a frequency of 0 Hz. … DC magnetic fields can also be created from a DC power source of electricity such as battery power, solar power and wind power.
What is the principle of operation of DC generator and derive its emf equation?
DC generator operates on the principle of the dynamically induced electromagnetic force. When a conductor is placed in a varying magnetic field, an electromotive force gets induced within the conductor. This induced e.m.f magnitude is measured using the equation of the electromotive force of a generator.
What are 5 sources of EMF?
The five sources of EMF are: Electromagnetism, Photoelectric, Thermoelectric, Piezoelectric and Chemical.
Is back EMF AC or DC?
Back EMF can have either a sinusoidal (AC) or a trapezoidal (DC) waveform. The shape of the back EMF is important, as it determines the type of drive current and commutation method that should be used for the motor.
What’s the full form of EMF?
Electromotive force (EMF) is equal to the terminal potential difference when no current flows. … EMF (ϵ) is the amount of energy (E) provided by the battery to each coulomb of charge (Q) passing through.
What is meant by back EMF?
Counter-electromotive force (counter EMF, CEMF), also known as back electromotive force (back EMF), is the electromotive force (voltage) that opposes the change in current which induced it. CEMF is the EMF caused by magnetic induction (see Faraday’s law of induction, electromagnetic induction, Lenz’s law).
What are three sources of EMF?
Devices that can provide EMF include electrochemical cells, thermoelectric devices, solar cells, electrical generators, transformers, and even Van de Graaff generators. In nature, EMF is generated whenever magnetic field fluctuations occur through a surface.
What is SI unit of EMF?
Electromotive force = amount of work done / quantity of charge transferred. So, the unit of emf = Joule/ coulomb.
What is back emf of DC motor?
When armature of dc motor rotates, the armature conductors move through the magnetic field, emf is induced in them. The induced emf acts in opposite direction to applied voltage. This voltage is known as back emf.
Why back emf is used in DC motor?
When the armature of the DC motor rotates under the influence of driving torque, the armature of the conductors moves through a magnetic field inducing an emf in them. The induced emf is in the opposite direction to the applied voltage and is known as the back emf.
What does back emf depend on?
The back EMF depends, of course, on the speed of the motor — the change in magnetic flux that generates it increases with motor speed — so that as the motor begins to turn, the back EMF grows until the motor has reached its maximum speed, at which point the back EMF stays at its maximum value.