Electricity

Subject: Science

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Overview

An instrument or a device that changes a non-electrical energy into electrical energy is called the sources of electricity. The electricity that is possessed due to change in the number of electrons in bodies is called current electricity. This note provides an information about electric charge, sources of electricity, electric circuit, conductor and insulators, conventional current flow, ammeter and galvanometer.
Electricity

Electric charge

Electric charge is defined as the electrical property of particle or a body. The process of producing electricity by rubbing is called electrification by friction.

Examples:

  • When a plastic comb is rubbed against dry hair, it attracts light objects. That is, a plastic comb rubbed on dry hair is charged.
  • When a glass rod is rubbed on silk, the glass rod is charged.
  • An ebonite rod gets electrified when it is rubbed on fur.

Static and current electricity

Static electricity: The electricity that is possessed due to change in the number of electrons in bodies.

Current electricity: The electricity that is possessed due to flow of electrons in conductors.

Difference between static and current electricity

Static electricity Current electricity
The electricity that is possessed due to change in the number of electrons in bodies. The electricity that is possessed due to flow of electrons in conductors.
It is produced in insulators. It occurs in conductors.
It cannot be transported from place to place through conducting wires. It can be transported from place to place through conducting wires.

Sources of electricity

An instrument or a device that changes a non-electrical energy into electrical energy is called the sources of electricity. Heat energy, chemical, mechanical energy, atomic energy etc. can be converted into electrical energy.

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Cells

The devices, which convert chemical energy into electrical energy, are called cells. Common use of cells in daily life is due to following reasons:

  • They are available in a portable form.
  • They produce direct current.
  • They can produce even a small amount of current, which is essential for some appliance.

Photocell

A photocell is a device, which converts light energy into electrical energy.

Generators or dynamo

Generators or dynamo are those devices which convert mechanical energy into electrical energy. Mechanical energy can be obtained from thermal energy, atomic energy, running water etc.

Electric circuit

The conducting path through which electricity flows is called electric circuit. An electric circuit, through which electricity flows, is called a closed circuit. An electric circuit, through which electricity does not flow, is called open circuit. It consists of a key and a bulb or any electrical device.

Conventional current flow

At first, about the movement of flow of current, it was believed that positive charges would move from a positively charged body to a negatively charged body if they are connected by a conducting wire which was known as conventional current flow.
But in reality, electric current is the flow of free electrons which flow in just opposite direction of the conventional current flow. But also still today we use conventional current flow though it is opposite because many definitions and explanations related to electricity are made on the basis of conventional current flow.

The rate of flow of charges through a conductor is called electric current.

If one coulomb charge flows through a conductor in one second, electric current is said to be one ampere.

Ammeter

An ammeter is an electrical device which measures the electric current flowing through a circuit.

Galvanometer

The galvanometer is an electrical device which detects the presence of current in an electric circuit.

Conductor and insulator

It is not that every substance or things conduct electricity. Some may conducts electricity but some may not. Those substances which conducts electricity are called conductors. Some examples of conductors are silver, copper, aluminium, graphite, etc. Those substances which do not conduct electricity are called insulators. Some examples of insulators are paper, wood, plastic, etc.
There are also substances which cannot conduct electricity at room or normal temperature but they can conduct electricity at high temperature. These substances are known as semi- conductors. Germanium and silicon are good examples of semi- conductors.

Things to remember
  • Electric charge is defined as the electrical property of particle or a body.
  • The electricity that is possessed due to change in the number of electrons in bodies is called current electricity.
  • The electricity that is possessed due to flow of electrons in conductors is called static electricity.
  • An instrument or a device that changes a non-electrical energy into electrical energy is called the sources of electricity.
  • The devices, which convert chemical energy into electrical energy, are called cells.
  • Generators or dynamo are those devices which convert mechanical energy into electrical energy.
  • The conducting path through which electricity flows is called electric circuit. An electric circuit, through which electricity flows, is called a closed circuit.
  • Ammeter is an electrical device which measures the electric current flowing through a circuit.
  • Galvanometer is an electrical device which detects the presence of current in an electric circuit.
  • It includes every relationship which established among the people.
  • There can be more than one community in a society. Community smaller than society.
  • It is a network of social relationships which cannot see or touched.
  • common interests and common objectives are not necessary for society.
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Questions and Answers
The phenomenon of continuous flow of electrons is known as electricity. Its types are:
  1. Static electricity
  2. Current electricity
The electricity produced by electric charges at rest is called static electricity. Eg. Charges on plastic, comb, glass rod, etc.
The electricity which flows from one point to other with the help of media is called current electricity. Eg: charges flow from a copper wire
When a body is rubbed against another body, they gain a property of attracting small bodies such that the bodies possess electric charge. They are of two types:
  1. Positive charge
  2. Negative charge
As we know that atom consists of proton (positive charge) and electron (negative charge) and neutron (charge less). In an atom, the number of positive charges and negative charges is equal such that the net charge is 0. Hence, an atom is electrically neutral.
If electrons transfer from one body to another by any means, one body has excess of electrons and the other body becomes deficient in electrons. The body which has excess of electrons is said to be negatively charged and another body which has deficiency of electrons is said to be positively charged. In this way, body becomes charged.
Electrons and protons both are charges but there is transformation of electron rather than proton because proton is about 1836 times heavier than an electron and protons are situated in the nucleus of an atom and not at the surface.
Those instruments that generate electricity are called the source of electricity. For example: photo cells, cells, generators or dynamo, etc.
Photo cell is a device which converts light energy into electrical energy. Its two advantages are:
  1. It uses everlasting solar energy.
  2. Its use does not pollute the environment.
In hydropower stations, electrical energy is not produced by burning any types of fuels but there is use of kinetic energy contained in moving water so that there is nothing to be ejected into the environment which makes it a pollution free source of electricity.
The rate of flow of charges through a conductor is called current.
i.e. Current (I) =

Its SI Unit is coulomb per second Cs-1 or Ampere(A).
If one coulomb charge flows across a conductor in one second, the current is said to be 1 ampere current.
The path through which an electric current flows is known as electric circuit. The components of an electric circuit are:
  1. source
  2. load
  3. wire
Conductors Insulators
Those substances that allow heat and electricity to flow through them are called conductors. Those substances that do not allow heat and electricity to flow through them are called insulators.
There are free electrons on its surface.
Example: brass, copper, etc.
There are not free electrons in this surface
Example: glass, silk, rubber, etc.
Quiz

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