DC NETWORK THEOREM - ELECTRICAL ENGINEERING BASIC

Current: “Rate of flow of electric charge.”

time

Charge

I = Coulombs/Sec or Ampere

Note:-

1. Direction of current is same as the direction of motion of +Ve charge or opposite to the direction of

motion of –Ve charge.

Voltage: “Energy required in transferring a charge of one coulomb from one point to

another point.”

Charge(Q)

Energy(W)

V = Joule/Coulomb or Volts

EMF (Electromotive force): “The EMF of a voltage source is the energy imparted by

the source to each coulomb of the charge passing through it.”

Charge(Q)

Energy(W)

E = Joule/Coulomb or Volts

Potential Difference: “The pd between two points is the energy required in transferring a

charge of coulomb from one point to another point.”

Charge(Q)

Energy(W)

pd = Joule/Coulomb or Volts

Voltage drop: “The voltage drop between two points is the decrease in energy required

in transferring a charge of coulomb from one point to another point.”

Charge(Q)

Energy(W)

Voltage drop = Joule/Coulomb or Volts

Resistance: “Electric resistance is the property of material which offers opposition to the

flow of current and dissipates energy.”

a

l

R = ñ Ohm or _ (Law of resistance)

Where l = Length of the wire

a = cross − sectional area of the wire

ñ = Resistivity or Specific Resistance of the material

Note:-

1. Resistance also depends on temperature.