What is Q-factor or Quality factor ?

# Q- factor measures the quality of a circuit or the sharpness of resonance means how the sharp circuit is . The more sharpness , the circuit has more tendency to receive a particular signal.

# Defination of Q factor .

It is defined as the ratio of the resonant frequency to the the band width frequency at which the current is reduced to 70% of the resonant current .

To understand it clearly .

Renonant frequency - in this frequency current is maximum in the circuit .

Bandwidth frequency - it is the frequency at which current is reduced to 70% of the resonant current (You may find w1 and w2 in the book , the w1 and w2 may has different frequency but at this frequency current is reduced to 70% of the resonant frequency ) . So, more the value of Q , the band width tries to become small vallue and sharpness of resonance increases .

Also , there are many definations .

Here , i do not claim what i said , its true . Good luck .

#

Q means Quality Factor, a factor which determines the efficiency of an LCR circuit.

A circuit which contains only L (inductor) and C (capacitor) works as a Harmonic Oscillator (or an undamped harmonic oscillator). Adding an ohmic resistance R makes it a Damped Harmonic Oscillator since it is responsible for energy dissipation.

Ohmic resistance R in LCR circuit also causes damping and thus dissipates energy in the oscillator)

The oscillations in this LCR circuit involves transfer of energy from capacitor ( in the form of electric field) to inductor ( in the form of magnetic field) and back to it again and again. 

But don't forget there is R also present there, when it comes to play, and as oscillations proceed, the energy remaining in the fields gradually diminishes or dissipates ( due to damping nature of ohmic resistance in this LCR circuit)

q factor simply means how efficient a system is , higher q factor means low energy loss. for example q factor of inductor is the ratio between the inductive reactance and ohmic resistance, in which higher inductive reactance means less power loss.

Q factor is a dimensionless parameter that describes how underdamped an oscillator or resonator is, and characterizes a resonator's bandwidth relative to its center frequency.