# What is Form factor? Form factor Formula

Form factor is defined as the ratio of RMS value to the average value of a waveform. The waveform can be quantity like voltage, current, etc. This parameter is generally used in the rectifiers.

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## Form factor Formula

$\text{Form factor}=\frac{{A_{rms}}}{{A_{avg}}}$

where,

Arms is the rms value of the waveform

Aavg is the average value of the waveform

### Form factor of Half wave rectifier

The RMS value of output current of single-phase half-wave rectifier is given by

$I_{rms}=\frac{I_{m}}{2}$

where, Im is the peak value of output current.

The average value of output current of single-phase half-wave rectifier is given by

$I_{avg}=\frac{I_{m}}{\pi}$

where, Im is the peak value of output current.

As we know that form factor is given by

$\text{Form factor}=\frac{{I_{rms}}}{{I_{avg}}}$

Therefore, we get

$\text{Form factor}=\frac{{\frac{I_{m}}{2}}}{{\frac{I_{m}}{\pi}}}$

∴ Form factor = π/2 = 1.5707963

The form factor of half wave rectifier is 1.5707963

### Form factor of Full wave rectifier

The RMS value of output current of single-phase full-wave rectifier is given by

$I_{rms}=\frac{I_{m}}{\sqrt{2}}$

where, Im is the peak value of output current.

The average value of output current of single-phase full-wave rectifier is given by

$I_{avg}=\frac{2I_{m}}{\pi}$

where, Im is the peak value of output current.

As we know that form factor is given by

$\text{Form factor}=\frac{{I_{rms}}}{{I_{avg}}}$

Therefore, we get

$\text{Form factor}=\frac{{\frac{I_{m}}{\sqrt{2}}}}{{\frac{2I_{m}}{\pi}}}$

∴ Form factor = 1.11072073

The form factor of full wave rectifier is 1.11072073

### Form factor of Bridge rectifier

The RMS value of output current of Bridge rectifier is given by

$I_{rms}=\frac{I_{m}}{\sqrt{2}}$

where, Im is the peak value of output current.

The average value of output current of Bridge rectifier is given by

$I_{avg}=\frac{2I_{m}}{\pi}$

where, Im is the peak value of output current.

As we know that form factor is given by

$\text{Form factor}=\frac{{I_{rms}}}{{I_{avg}}}$

Therefore, we get

$\text{Form factor}=\frac{{\frac{I_{m}}{\sqrt{2}}}}{{\frac{2I_{m}}{\pi}}}$

∴ Form factor = 1.11072073

The form factor of bridge rectifier is 1.11072073

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