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WORKSHOP SCIENCE - CITS

EXERCISE 9 : Electricity

Electricity is the flow of electrical power or charge. It is a secondary energy source which means that we get
it from the conversion of other sources of energy, like coal, natural gas, oil, nuclear power and other natural
sources, which are called primary sources.
There are basic types of sources used in electricity are Fossil fuels, Renewable energy, Mainly hydroelectric,
Nuclear power. Talking about the SI unit of electricity, it is represented by the unit of power which is Watt.

The formula for electrical energy is E = V*I*t joules, where V is the potential difference, I is the current and t is
the time. The formula for electrical power is Power (P) = V*I watts, where V is the potential difference and I is the
current.
An ampere is a unit of measure of the rate of electron flow or current in an electrical conductor. One ampere of
current represents one coulomb of electrical charge (6.24 x 1018 charge carriers) moving past a specific point
in one second. One Volt is defined as energy consumption of one joule per electric charge of one coulomb. 1V
= 1J/C. One volt is equal to the current of 1 amp times the resistance of 1 ohm. Ohm’s Law is V = IR, where V =
voltage, I = current, and R = resistance.
Basic definitions like EMF:

Electromotive force is defined as the electric potential produced by either an electrochemical cell or by changing
the magnetic field. EMF is the commonly used acronym for electromotive force. Electromotive force is the
characteristic of any energy source capable of driving electric change around a circuit. It is abbreviated E in the
international metric system but also, popularly, as emf.EMF formula can be expressed as, e = IR + Ir or e = V+ Ir,
where, e is the electromotive force (Volts), I = current (A), R = Load resistance, r is the internal resistance of the
cell measured in ohms.
Current: Electric current is defined as the rate of flow of electrons in a conductor. The SI Unit of electric current
is the Ampere. Electric current refers to flow of electricity in an electronic circuit, and to the amount of electricity
flowing through a circuit. It is measured in amperes (A). The larger the value in amperes, the more electricity is
flowing in the circuit. The SI unit of current is ampere which measures the flow of electric charge across a surface
at the rate of one coulomb per second.
Voltage: Voltage is the force that makes electrons flow. It’s difference in potential energy between two different
points in a circuit.
Current: Current is the rate of the flow of electrons. It’s measured in amperes, which are also called amps. Power
(Watts): The power used in a circuit is measured in watts.
Resistance: Resistance to electricity–that is, electrical resistance–is a force that counteracts the flow of current.
In this way, it serves as an indicator of how difficult it is for current to flow. Resistance values are expressed in
ohms (Ω).

V = I X R
R= V/I
R= Resistance, V= Volt, I = Current.
Potential difference: Electric potential difference is a measure of the amount of potential energy at a given
location in a circuit. The concept is also known as “voltage” and is typically measured in “volts.” One can think of
electric potential difference (and voltage) as a measure of electron pressure.

voltage is called potential difference because it is a measure of the difference in potential energy between two
points in a circuit. This potential difference, or voltage, is present even when a circuit is not switched on, similar
to how a brick held in the air has gravitational potential energy.
The S.I. Unit of potential difference is Volt. The potential difference between two points is said to be 1 volt if work
is done in transferring 1 coulomb of charge from one point to other point is 1 Joule.

Uses of Electricity: A large amount of electricity is currently being used for street lighting in almost every
country. More uses in sectors as follows:

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