Alternating Current

(5)

Alternating Current

The electric current whose flow is not unidirectional moreover it alternates at a frequency, is called alternating current. In other words, the direction of the electric current continuously changes from forward to backward and then backward to forward in the circuit. The number of times, this direction changes from forward to backward or from backward to forward per second, is referred as frequency of the current. The electric current produced in an alternator is always an alternating current. The shape of the waveform of an alternating electric current is usually sinusoidal. But square, triangular and other types of waveform are also available for attending current.

Conventional Direction of Alternating Current

As direct current, alternating electric current is denoted with arrow. An AC has both forward and backward direction of flow. The arrow head always indicates the forward direction of the current. In different point of view, when the electric current has a positive valve, the direction of electric current is same as the reference arrow and when the electric current gets negative value; its direction is just opposite of the reference arrow.

Effects of Electric Current

There are mainly two effects of electric current, such as heating effect and magnetic effect. Each and every utilization of electricity, we see in our daily life, is either due to heating effect or due to magnetic effect of electric current. For examples, the light bulb glows in our house is due to heating effect of electric current and the fan rotates in our house is due to magnetic effect of electric current. There are thousands of other examples which can illustrate the effect of electric current, too.

Heating Effect of Electric Current

Whenever electric current passes through a conductor there would be a generation of heat due to ohmic loss in the conductor. This is commonly known as heating effect of electric current.

Since, we cannot use electric power directly, we need to convert it into another usable power, like heat, light, or mechanical power etc. When electric current flows through a conductor some loss occurs and this loss is almost inevitable, and more the resistance of the conductor, more the loss. This loss due to the electrical resistance of conductor is mainly responsible for the heating effect of electric current.

As some electric power is converted into heat energy, this phenomenon can be described by Joule's law, which states that,

Where H is the generated heat in calories, "i" is the electric current that is flowing through the wire and it is measured in amperes, "r" is the resistance of the conductor in ohm(Ω) and "t" is the duration of electric current flowing in seconds. If we know the time of electric current flowing, the resistance of wire, and amount of electric current flow, we can easily find out the generated heat of the circuit. This heat can be utilized in various ways. 

We saw that the more the electrical resistance of the wire the more the generated heat in the circuit, but to know more accurately about the heating effect of current, we should know about it from the atomic level. As the flow of electric current is nothing but the flow of electrons there will always be resistance from the fixed atoms of the conductor. The fixed atoms of the wire resist the flow of electrons and as a result there are collisions and as the kinetic energy converts into heat energy we see that the wire is getting hot.