Page 155 - Electrician - TT (Volume 1)

ELECTRICIAN - CITS

Similarities between electrical and magnetic circuits are given below

Electric Circuit Magnetic Circuit
Path traced by the current is known as electric current. Path traced by the magnetic flux is called as magnetic
circuit.
EMF is the driving force in the electric circuit. The unit MMF is the driving force in the magnetic circuit. The
is Volts. unit is ampere turns.

There is a current I in the electric circuit which is There is flux φ in the magnetic circuit which is measured
measured in amperes. in the weber.

The flow of electrons decides the current in conductor. The number of magnetic lines of force decides the flux.

Resistance (R) oppose the flow of the current. The unit Reluctance (S) is opposed by magnetic path to the
is Ohm flux. The Unit is ampere turn/weber.

R = ρ. l/a. S = l/ (μ0μra).
Directly proportional to l. Directly proportional to l. Inversely proportional to μ =
Inversely proportional to a. μ0μr.
Depends on nature of material. Inversely proportional to a

The current I = EMF/ Resistance The Flux = MMF/ Reluctance

The current density The flux density

There are few dissimilarities between the two circuits which are listed below:

Electric Circuit Magnetic Circuit

In the electric circuit, the current is actually flows. Due to mmf flux gets established and does not flow in
ie, there is movement of electrons. the sense in which current flows.

There are many materials which can be used as There is no magnetic insulator as flux can pass
insulators (air, PVC, synthetic resins etc) which through all the materials, even through the air as well.
current cannot pass

Energy must be supplied to the electric circuit to Energy is required to create the magnetic flux, but is
maintain the flow of current. not required to maintain it.

The resistance and conductivity are independent of The reluctance, permanence and permeability are
current density under constant temperature. But may dependent on the flux density.
change due to the temperature.
Electric lines of flux are not closed. They start from Magnetic lines of flux are closed lines. They flow from
positive charge and end on negative charge. N pole to S pole externally while S pole to N pole
internally.

There is continuous consumption of electrical energy. Energy is required to create the magnetic flux and not
to maintain it.

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CITS : Power - Electrician & Wireman - Lesson 26-29