What is Alternating Current? Learn the Basics of it

Transmission of Alternating Current

Here is how alternating current comes to us in our day-to-day life. These are some basic information that will keep you aware of how alternating current is running the world. 

Firstly, Europe and most of the world use a standard of 220 volts roughly and 50Hz of alternating current in their power grid. Secondly, the USA and some other regions use a standard of 120 volts and 60Hz of alternating current. Thirdly, countries like Japan use both of the standards in their grids.

One other example of alternating current is audio and radio signals that pass through electric wires. Moreover, for industrial use, the standard use of alternating current voltage is 415V. 

Aircraft, spaceship, marine, military, and applications use 400Hz of alternating current. These are the sensitive application and where light equipment and higher motor speed is necessary. 

Alternating current is easy to generate and suitable for power distribution. This is because AC can easily be transformed from a higher voltage level to a lower voltage level. In other words, the alternating voltage can easily be stepped up or down to a required voltage level. 

In order to reduce energy loss during transmission, electrical power is transferred at higher voltage and lower current. Moreover, this helps to transfer electric power over a certain long-distance through electric grids. The power is later stepped down just before being distributed for normal day-to-day electricity use.

Wire for Alternating Current

The majority of the Power Grids are for AC. Therefore, all generators of AC that are in connection with the power grid must be in sync with each other. The equipment that uses AC current usually have three kinds of wire:

1. A hot wire that transmits the current.
2. A Neutral wire that creates a return path for the current in the hot wire. It also has a connection to the earth.
3. The third wire is the ground wire which also has a connection to the earth. The wire has a connection to the metallic part of the equipment. It ensures that electrical safety and eliminates electric shock hazards.

However, most of the electronic gadgets that we use receive the alternating current and transform it into direct current. This is because most devices like smartphones and laptops run on a battery which uses direct current. Therefore, alternating current can damage the battery and also the gadget. 

How to Produce Alternating Current?

You can produce alternating current with the help of a device, Alternator. The alternator is a special kind of electronic generator that produces alternating currents. Moreover, the alternator consists of a magnet and a loop of wire. In the alternator, the wire loop is spun inside a magnetic field. As the loop of wires spun, it induces a current through it. 

The rotation of the wire can happen through any kind of means, such as a wind turbine, steam turbine, flowing water, etc. The wire spins and enters different magnetic polarities at a regular interval. As a result, the voltage and the current alternate on the wire. 

To be more precise, as the wire spins in the magnetic field, the strength of the magnetic field changes through the wire, which creates a force. As a result, the electric charges start flowing around the wire.

Moreover, the force creates an electric current in one direction of the wire. But the wire loop rotates 180 degrees. As a result, the force reverses in the wire and create an electric current in the opposite direction around the wire. Therefore, every time the loop rotates 180 degrees, the force changes direction in the opposite way. As a result, the current flow also changes. These 180-degree change of direction of the force at a regular interval generates alternating current.

The alternator or the electric generator also have slip rings that ensure that the end of the wire is always connected with the same side of the electric circuit. As a result, the direction of current changes on every half rotation of the wire.

Alternating Current Vs Direct Current

In our everyday electricity use, we generally use two kinds of current mainly. We are already discussing alternating current, but the other one is direct current (DC). In order to define direct current, it is the flow of electric charge in one direction. Batteries, cells, rectifiers and generators with commutators produce direct current. 

Before we jump into comparison, we need to understand how both kinds of electric current causes losses. This will help us understand what kind of electric current must be used in what type of situation.

The alternating current had specific advantages over direct current for decades. Firstly, the transmission of AC was more efficient over large distances without too much loss of energy to resistance. Changing the current voltage was difficult using the first DC electric power grid during the late 19th century. As a result of too much power loss, these grids was maintaining low voltage and high current, and only short distance transmission was possible. 

Therefore, the AC system soon replaced DC power transmission. AC power can transmit at a high voltage and low current, and we can easily change the voltage with help of a transformer. But DC system can quickly change voltage as well. But modern AC systems can transmit powers from generators with hundreds and thousands of voltage. The voltage is then lowered from 120 volts to 220 volts for general domestic and commercial use. 

However, many electric gadgets prefer direct current to alternating current for safety reasons, smooth flow of current and even voltage. But AC current in power outlets can be transformed into DC as it enters the electronic gadgets. 

Power Loss for Both Form of Electric Current

In order to transfer electricity over very long distances, DC current is more suitable than AC current. The charging current is very high for AC which causes I2R loss.

In a theoretical circuit, all the power that goes into an input terminal reaches the critical load without any energy loss. It doesn’t dissipate in the wiring component that comes along the path. But in a real circuit, is always a minimum amount of resistance where some amount of power is lost. This occurs in both AC and DC supplies, which cause electrical losses, and the dissipation occurs as heat. You can calculate the loss of electricity in the following way.

According to Ohm’s Law: V = IR where V = voltage (Volts) across a component, R is the resistance (in Ohms) of a component, and I is the current in Amps through the component.

Power Law: W = VI where V and I are similar as above, and W = power dissipated in Watts.

After we combine these two laws, we can find the loss W=(IR)I or I2R.

It is known as Copper loss. The reason behind explaining all this formula is that this copper loss can be more in AC circuits like transformers. However, more losses also happen due to induced current that flows through the resistance of the component’s iron core. It is called core losses.

Copper losses in transformers and motors can be decreased by increasing the cross-sectional area of the conductor, improving the winding technique, and adopting materials with higher electrical conductivities.

The proximity effect and skin effect cause the current to be unevenly dispersed across the conductor at high frequencies, increasing the conductor’s effective resistance.  Litz wire can distribute current uniformly across its cross-section.