Electrical units

The main units that are used in electrical engineering are those relating to current, potential or voltage, resistance, power and energy.

Current is that which flows in the conductors and form the electricity. It is measured in amperes. Potential, voltage, or electromotive force is that which causes a current to flow between tow points when they are connected by conductor. Their unit is volt.

The total potential which are generated by a cell or generator is called its electromotive force ( e.m.f ). The difference in potential between any tow points in the circuit is simply known as the voltage. The opposition which a substance offers to the flow of current through it is called its resistance. Substances that have a small resistance, such as metals or some liquids, are called conductors. And those offer a high resistance are called insulators. The unit of resistance is the ohm. The mega ohm is equaled one million ohm.

When resistances are connected top form a close circuit, they are said to be connected in series. The total resistance of such as a circuit is the sum of all the resistances. The resistances that are connected to the same terminals are said to be in parallel.

In a close circuit, there is a relation between the current, voltage, and resistance. And this is expressed by what is known as ohm's law.

The law is represented by the following equation:

I = U/R

The power in a d.c circuit is found from the product of the amperes in the circuit and the voltage of its terminal. The unit of power is watt. The practical unit of electrical energy is kilowatt-hour. It is the energy that is transformed in a circuit when the power is one kilowatt and the time taken out is one hour.