Definitions [8]
Electromagnetic induction is the production of an electromotive force across an electrical conductor in a changing magnetic flux or magnetic field.
The circulating currents induced in conductive materials (bulk pieces of conductors) when the magnetic flux linked with them changes, due to exposure to changing magnetic fields, are called eddy currents.
An a.c. generator is a device which converts the mechanical energy into the electrical energy using the principle of electromagnetic induction.
Define a Transformer.
The transformer is a device used for converting low voltage into high voltage and high voltage into low voltage. It works on the principle of electromagnetic induction.
An electrical device which converts low alternating voltage at high current to high alternating voltage at low current (or vice versa) — i.e., a device which reduces or increases the voltage in an AC circuit through mutual induction — is called a transformer.
Give any one definition of power factor.
The Power Factor is the ratio of True Power (measured in Watts) to Apparent Power (measured in Volt-Amperes) in an AC circuit.
Power factor (cos Φ) = `"True power"/"Apparent power"`
In the expression Pav = VrmsIrms cos ϕ, the quantity cos φ is called the power factor.
The current flowing in a purely inductive or purely capacitive circuit for which cos φ = 0 and no power is dissipated even though the current is flowing is called wattless current.
Formulae [4]
Eddy current: i = \[\frac {\text {Induced emf (e)}}{\text {Resistance (R)}}\]
Pinput = Poutput
P = VI = \[\frac{V_mI_m}{2}[\cos\phi-\cos(2\omega t+\phi)]\]
Pav = VI cos ϕ = I2Z cos ϕ = \[\frac {V_mI_m}{2}\]cos ϕ = VrmsIrms cos ϕ
Theorems and Laws [1]
A transformer is based on the principle of mutual induction, i.e., whenever the magnetic flux linked with a coil changes, an emf is induced in the neighbouring coil. For an ideal transformer there is no loss of power, so Pinput = Poutput. On the basis of winding, transformers are of two types — step-up and step-down.
