Physics Notes For SSC CGL / CHSL Exam 2019-20 on : Types of Electrical Current

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An electric current is a flow of electric charge in a circuit. More specifically, the electric current is the rate of charge flow past a given point in an electric circuit. The charge can be negatively charged electrons or positive charge carriers including protons, positive ions or holes.

The magnitude of the electric current is measured in coulombs per second, the common unit for this being the Ampere or amp which is designated by the letter ‘A’.

Alternating Current (AC)

Alternating current is defined as the flow of charge that changes direction periodically. The result obtained will be, the voltage level also reverses along with the current. Basically, AC is used to deliver power to industries, houses, office buildings, etc.

Generation of AC

AC is produced by using called an alternator. It is designed to produce alternating current. Inside of a magnetic field, a loop of wire is spun, from which induced current will flow along the wire. Here the rotation of the wire may come from any no of means i.e. from, a steam turbine, flowing water, a wind turbine and so on. This is because of the wire spins and enters into different magnetic polarity periodically, the current and voltage alternate in the wire.

From this, the generated current can be of many waveforms like sine, square and triangle. But in most of the cases, the sine wave is preferred because it is easy to generate and calculations can be done with ease. However, the rest of the wave requires an additional device to convert them into respective waveforms or the shape of the equipment has to be changed and the calculations will be too difficult. 

Applications of AC

• Home and office outlets are used AC.
• Generating and transmission of AC power for long distances are easy.
• Less energy is lost in electrical power transmission for high voltages (> 110kV).
• For higher voltages imply lower currents, and for lower currents, less heat is generated in the power line which is obviously due to low resistance.
• AC can be easily converted from high voltage to low voltage and vice versa with the help of transformers.
• AC power the electric motors.
• It is also useful for many large appliances like refrigerators, dishwashers, etc.
• Direct Current

Direct current (DC)

In this type the current flows in only one direction, advantages of this type of current is that it is very easy to store because almost all type of batteries uses direct current, most of the electronics use direct current, computers, telephones, satellites all work on DC.

The main Difference between AC and DC is discussing in the following comparison chart