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Unit – Electricity

Fundamentals of electricity:

Work: is said to be done when a force is exerted on a body and the body changes its position.

W = F X d   where, W is work done , F is the force applied and d  is the displacement , SI unit of work is

 joule.

Power: power is defined as the work done or energy released or consumed in unit time.

P = W/t Where, P is power, W is work done and t is the time. SI unit of power is J/s or watt. 

Energy: it is the inherent ability of an object to do work. There are different forms of energy in a body

for e.g. Mechanical energy, kinetic energy, chemical energy, electrical energy, potential energy. SI unit

of energy is joules.

Kinetic energy: the kinetic energy of an object is defined as the work needed to bring a body in motion

from its state of rest.

Potential energy: it is the energy which is stored within the physical system. This energy can be released

or converted into other forms of energy. For e.g., when a fuel is burned, chemical energy is converted

into heat.

Electricity: it is the flow of electrical power or charge. it is a secondary energy source , means we get it

from the conversion of other sources of energy such as coal, natural gas, etc. whenever two points

having electrical potential difference are connected by a conductor, electricity flows.

Electrical quantities:

Current: it is the flow of electrons in any conductor. it is represented by the symbol I. SI unit of current isAmpere . Flow of one coulomb charge in one second is one ampere. (1Amp  1coulomb/sec)

Volts: it is the force or pressure (potential difference) that causes the flow of electrons in any closed

circuit. The unit of this force is volts (V). The difference of the electrical voltage between any two points

is called the Potential Difference 

Resistance: it may be defined as that property of a substance which opposes the flow of electricity

through it. The unit of resistance is ohm ( )

Open circuit & closed circuit : refer class notes

Series circuit, parallel circuit & reasons for putting appliances in parallel circuit: class notes

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AC [alternating current] & DC [direct current]: class notes

Advantages of AC:

1.  AC voltage can be increased or decreased with the help of transformers.

2.  AC motors are cheaper, light in weight; require lesser space as compared to DC motors.

3.  AC can be converted to DC easily, but the reverse cannot be done.

Advantages of DC:

1.  DC motors are most suitable for tram cars, lifts and in circuit breakers.

2.  Arc lamps for search lights and cinema projectors work in DC.

3.  Solar cells produce DC.

Electrical wiring:

Electrical wiring is used to carry electric supply to the premises and distribute it at various locations.

Cleat wiring: this type of wiring is suitable for temporary wiring purposes such as in marriage halls .its

saves labour and overall costs. VIR or PVC wires are normally used in this sysytem of wiring.

This type of wiring can be dismantled very quickly. They are not recommneded for permanent

installations.

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Wooden batten wiring : in this type of wiring either TRS or PVC wires are used. Here the wires are carried

on wooden batten with clips. This is very popular in domestic wiring. Ease of installation and less costly.

This type of wiring is suitable in damp climate , but cannot withstand much haet and fire hazards.

Casing and capping wiring: it is used for indoor and domestic installations.

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Lead sheathed wiring :

Conduit wiring

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