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- W = Watt
- J = Joule
- S = Second

,

Where:

- M = Mutual inductance in Henrys
- k = coefficient of coupling
- L_1 Inductance of first winding
- L_2 Inductance of second winding

For Iron Core ,

Where:

- p subscript refers to Primary winding
- s subscript refers to secondary winding
- N = number of turns

Where:

*F*= repulsive force*r*= distance between poles- μ permeability ( μ of air = 1)
*H*= Magnetizing Force in Oersted*m**m**f*= Magnetic Motive Force - in Gilberts- Orested = Gilberts/CM
- β = Flux density in Gauss
- φ = Total flux density in Maxwells
*r*= Reluctance*P*= Permeance

*m**m**f* = φ*R*

,

Where

*X*_{L}refers to inductive reactance*X*_{C}refers to capacitive reactance

Τ = time in seconds to 2/3 rise

Τ = *R**C*

Deviation = modulating index Deviation ratio = Deviation / highest modulating frequency

- Zero_Gain_Amps
- Current gain

*I*_{c}=*I*_{b}β

or

- Where

β = beta </math> *I*_{b} = Base current *I*_{c} = Collector current

- Transconductance
- Transconductance is a contraction of transfer conductance. The old unit of conductance, the mho (ohm spelled backwards), was replaced by the SI unit, the siemens, with the symbol S (1 siemens = 1 ampere per volt).

For small signal alternating current, the Transconductance is estimated:

Where :

*g*_{m}= small signal transconductance- Thermal voltage
*k*Boltzmann constant ,*I*_{cq}= quiescent point, Q-point, or bias point

Distortion begins somewhere once the base voltage exceeds about 5 to 15mVp-p

If we look at large signals we must use

Where :

*G*_{m}= Large signal Transconductance (not to be confused with*g*_{m}

- Small-signal-input-resistance (
*R*_{π})for a common emitter amp with the emitter AC grounded:

Which means that input resistance goes up with β

- Large-signal-Input-resistance (
*R*_{Π})for a common emitter amp with the emitter AC grounded:

- (approximately 26 mV at 300 K ≈ room temperature).

where

*V*_{T}is the Boltzmann constant*k**T*/*q**q*Electronic Charge*T*Temperature in K*I*_{E}is the emitter current*I*_{C}is the collector current- α
_{F}is the common base forward short circuit current gain (0.98 to 0.998) *I*_{ES}is the reverse saturation current of the base–emitter diode (on the order of 10^{−15}to 10^{−12}amperes)*V*_{BE}is the base–emitter voltage

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