Electric Current Classification of Electric Current, Electrical Work, Power, Energy

Electric current

Direct current (D.C.)

1. Pulsating D.C.
2. Pure D.C.

Alternating Current (A.C.)

1. Sinusoidal
2. Other shapes

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Direct current (D.C.)

A direct current is the current which does not change its direction. It can be a pure d.c. or a pulsating d.c.

Pure DC :

Fig. 2.1 Waveform of pure D.C.

Pure dc does not change its direction with respect to time

Its value always remains constant with respect to time

Pulsating DC :

Its change the magnitude with respect to time. But polarity does not change.

Application of Direct Current

1. Batteries
2. DC motors
3. Torch
4. DC generators

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Alternating Current A.C.

An AC current is the one which changes its value as well as direction with respect to time.

Fig 2.2 Waveform of AC current

What is Alternating Current?

Both the direction and magnitude of alternating current changes.

Advantages of AC current

1. It is possible to use a transformer.
2. Distribution efficiency is high.
3. Generation is easy.
4. Installation is less costly.

Application of AC current

1. Alternators
2. Induction motors
3. Fans and lamps
4. All the domestic appliances

Comparison of direct current and alternating current

Parameter	Alternating Current	Direct Current
Waveform
Definition	An AC current is the one which changes its value as well as direction with respect to time.	A direct current is the current which does not change its direction. It can be a pure d.c. or a pulsating d.c.
Use of transformer	Possible	Not possible
Distribution Efficiency	High	Low
Application	Ac motors, domestic and industrial supply etc.	Dc machines, HVDC systems
Generation	Easy	Ac waveform using commutator or rectifier

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Effect of Electric Current

1. Magnetic effect
2. Chemical effect
3. The heating effect

Magnetic Effect

When electric current passes through conductor, a magnetic field devolve across the conductor and its act as an electromagnet.

If the coil wound on a magnetic material such as iron, then that piece act as a magnet.

Chemical Effect

DC current is passed through chemical solution the solution is decomposed into its constituent substances.

This process is called as the chemical effect.

Electrolytes: Electrolytes are the liquids which allow the electric current to pass through them.

Ionization: Ionization is the process of splitting up of molecules into positive and negative ions

Heating Effect

The heating element become hot due to flow of current through it and the heat

H = I²Rt

Where,

I = RMS current

R = Resistance of heating element

t = Time

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Concept of Electrical Work

Electrical work is work done to transfer a change from one point to other

Unit is Joules

W= V x I x t Joules

Concept of Power

The electric power due to voltage and current

It is defined as the product of voltage and current

Power P = V x I

P is measured in Watts

Concept of Energy

The electric energy defined as the product of power and time

Energy = Power(P) x Time(t)

S.I. Unit is Watt-second or joules

Alternative expression

E = V x I x t Joules

Direct current (D.C.)

A direct current is the current which does not change its direction. It can be a pure d.c. or a pulsating d.c.

What is Alternating Current?

Both the direction and magnitude of alternating current changes.

Advantages of AC current

1. It is possible to use a transformer.
2. Distribution efficiency is high.
3. Generation is easy.
4. Installation is less costly.