School

Electrical & Electronic

1. ELECTRICITY

Introduction :-

In today’s modern age, electricity has made its important place. Now we cannot survive without electricity. Whether it is used in mobile in the form of battery or it is running the fan in the house in the form of alternative current . If electricity disappears forever from today, we will all feel as we are living in ancient times.

ELECTRIC CURRENT AND CIRCUIT :-

The flow of anything is a Current, such as air or water. Similarly, If Electric charge flows through a conductor (for example: wire) then it’s called electric current.

Let us understand this with example :-

Just like we keep a battery in the right order then when both the points of the LED bulb are connected to the two points of the battery, the flow of charges starts and the bulb starts glowing.

You must have seen the torch in which when we switch on/off the light also goes on/off.

When we put the cell or battery in proper order and connect both the points of the battery to the two points of the bulb then it makes a continuous path then electric flow starts and the bulb starts burning.

Lets understand the switch in the torch :-

A switch makes a conducting link between the cell and the bulb.

The switch is installed in the positive wire of the battery.

When we turn on the torch, a connection is made between the battery and the bulb and then light starts coming out from the bulb.

and

When we turn off the torch, the connection between the battery and the bulb is broken and then the light from the bulb stops coming out.

A continuous and closed path of an electric current is called an electric circuit .

What is Electric Current ? Explain

The amount of charge flowing through a particular area in unit time is Electric Current .

In other words,

it is the rate of flow of electric charges. In circuits using wires (metallic) .

Electric current was considered to be the flow of positive charges .

Conventionally,

in an electric circuit the direction of electric current is taken as opposite to the direction of the flow of electrons, which are negative charges.

If a net charge Q, flows across any cross-section of a conductor in

time t, then the current I, through the cross-section is :-

The SI unit of Electric Charge is Coulomb (C) .

Unit of the Electric current is Ampere(A), Named after the French scientist Andre-Marie Ampere (1775-1836).

One ampere is constituted by the flow of one coulomb of charge per second, that is –

The device which measures electric current is called Ammeter.

Ammeter is always connected in series in a circuit where we have to measure the Current (Ampere) .

‘Flow’ of Electric charges inside a wire :-

Electric charge always flows on the surface of the conductor. When the electron starts moving, electric current starts flowing in the opposite direction. Electrons can move freely from one atom to another whether the conductor is solid or liquid.