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# Electrical Theory

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 Sub Topics Electrical theory deals with the theory related to the electricity, which constitutes electric charge, electric current, electric field etc. The important law related to this theory is Ohm's law. This reveals the relation between the voltage, resistance and current. Ohm's law is considered as the fundamental law in electricity. This section will helps to understand basic concepts of electricity, electric charge, current etc.

## Electric Charge

In general, we can say that electric charge is a physical property of a material. The peculiarity of the charge is that, it experience a force when a charged particle is placed in the field. There are two types of charges. One is positive and other one is negative. Like charge repels each other and unlike charge attracts each other. The SI unit of charge is given by Coulomb (C).

## Electric Current

As we know, the electric current is the flow of electric charge through a circuit. Not only the flow of charge but also it will generate because of the movement of ions or electrons. The notation of current is I. The unit is given by ampere. The expression for current is,
I = $\frac{Q}{t}$
where,
I is the current
Q is the charge
t is the time

There are two types of current. One is Alternative Current (AC) and other one is Direct Current (DC).

## Electrical Resistance

Electrical resistance is the opposition of the flow of current through a conductor. If the resistance is less, the material conducts more current. The equation for the resistance is given as,

R = $\frac{V}{I}$
where,
V is the voltage
I is the current

From the equation, it is clear that, resistance is directly proportional to voltage and inversely proportional to current. The unit of resistance is $\Omega$.

## Electromotive Force

Electromotive force or e.m.f is defined as the voltage generated when a circuit is connected to a external source. That is, the generation of voltage when a variation of magnetic field is present. It can be measured in terms of volts. This quantity is formulated using the Faraday's law.

## Electrical Power

Electrical power can be stated as, the rate of electricity transferred through an electrical circuit. It can be produced by electric generators by adopting different methods. And distributes through transformers for industrial and domestic applications.

Power can be measured in terms of voltage and current. the formula is,
P = V I
The unit is watts.

## Ohm's Law

Ohm's law is a fundamental law in electricity. It is defined as the current flowing through a current carrying conductor is directly proportional to the voltage and inversely proportional to resistance.

The mathematical representation is given by,

I = $\frac{V}{R}$

## Types of Current

The important types of current are Alternating current (AC) and Direct Current (DC).

1. Alternating Current (AC)

If the current changes its direction or polarity in positive or negative direction in particular time interval. Ac current is generated in power stations. The wave form is illustrated below:

2. Direct Current (DC)

If the direction of the current is constant the current is said to be direct current or dc. Dc current is produced by batteries. It is used for house hold applications. The dc wave form is depicted below: