ELECTRICITY , Class X, Part-1

                                                                                                              ELECTRICITY 

     Introduction

Electricity is an important source of energy in the modern times electricity is used in our homes, in industry and in transport. For example, electricity is used in our homes for lighting, operating fans and heating purposes. In industry electrics is used to run various types of machines and in transport sector electricity is being used to pull electric trains. In order to understand electricity we should first know something about electric charges. The flow of electric charges is called “electricity”. Electric charge of two type positive and negative charge.

   Types of electric charges

Electric charges of two type positive and negative charges. The charge acquired by glass rod when rubbed with a silk cloth is called positive charge. The charge acquired by an ebonite rod when rubbed with a woollen cloth is called negative charge.

                        An important property of electric charges

Opposite charges or unlike charges attract each other for example, a positive charges attracts. Similar charges or like charges repeal each other. This is also the fundamental law of electricity. For example, a positive repeal a positive charge and a negative charge repel a negative charge.

                      The S.1 unit of electric charge is coulomb.
Which is denoted by the letter C. One coulomb is that quantity of electric charge which exerts a force of 9x109 newtons on an equal charge placed at a distance of 1 meter from it.                   
Matter contains positively charged particles Called protons and negatively charges particles called electrons. A proton possesses a positive charge of 1.6 x 10-19C. Whereas an electron possess a negative charge of  1.6x10-19 C.
It is obvious that unit of electric charge coulomb is much bigger than the charge of a proton or an electron.
                          CONDUCTORS AND INSULATORS
All the substances can be divided mainly into two electrical categories, conductors and insulators.
Conductors
Those substances through which electric charges can flow are called conductors or Those substances through which electricity can flow easily are called conductors.
Example:- all metals like silver, copper and aluminium etc. The metal alloys such as nichrome , Maganin and constantan .
Metal alloys are also used in making heating elements of electrical appliances such as nichrome, maganin and constantan. In alloys electrical conductivity is much less than that of pure metals.
Carbon in the form of graphite is also a conductor. The human body plant (green) and animal body is a fairly good conductor.
Insulators

Those substances through which electric charges can’t flow are called insulators (Or) those substances through which electricity can’t flow are called insulators.Example glass, ebonite, rubber, plastic, paper, dry air, dry wood, cotton, mica, backelite, porcelain and dry leather are all insulators because they do not allow electric charges (electricity) to flow through them. All the conductors (like metals) have some electrons which are loosely held by the nuclei of their atoms. These electrons are called “free electrons” and can move from one atom to other atoms. Throughout the conductors.The free electrons or presence of free electrons in a substance make it a conductors (electricity).Electricity can be classified into two parts
1.    Static electricity
2.    Current electricity
The electrons present in insulators are strongly held by the nuclei of their atoms, since there are no free electrons in an insulator which can move from one atom to another, an insulator does not allow electric charges (electricity) to flow through it.


 Electric potential (v)

When a small positive text charge is placed in the electric field due to another charge, it experience a force. So work has to be done on the positive text charge to more it against this force of repulsion.

The electric potential (or potential) at a point in an electric field is defined as the work done in moving a unit positive charge from infinity to that point.
 Potential is denoted by the symbol V and its unit is volt. A potential of 1 Volt at a point means that 1 joule of work is done in moving 1 unit positive charge or 1 coulomb of charge from infinity to that point.

 Potential difference (P.D or V)

 The difference in electric potential between two points is known as potential difference.

The potential difference between two point  an electric circuit is defined as the amount of work done in moving a unit charge form one point to the other point.

Where,W = work done     
 Q = quantity of charge moved
The S.1 unit of potential difference  (P.D.) is volt (V).
 



Comments

Post a Comment

please do not enter any spam link in the comment box

Popular posts from this blog

FORCE AND LAWS OF MOTION, Class IX, Part 3

Image
                                         In order to understand Newton’s second law of motion, we should first know the meaning of the term momentum of a moving body (or moving object). We know that a cricket ball is much heavier than a tennis ball. Suppose we throw a cricket ball and a tennis ball, both with the same speed or velocity. It will be found that more force is required to stop the cricket ball (Which has more mass) and less force is required to stop the tennis ball (which has less mass). We conclude that the force required to stop a moving body is directly proportional to its mass. If we throw two cricket balls of the same mass at different speeds or velocities, it will be found that more force is required to stop that cricket ball which is moving with higher velocity and less force is required to ...
Read more

FORCE AND LAWS OF MOTION, Class IX, Part 4

Image
  If a boy wearing roller skates stands facing a wall and pushes the wall with his hands, the boy finds himself moving backward, away from the wall. It appears as if the wall also pushes the boy away. When the boy exerts a force on the wall by pushing it with his hands, then the wall exerts an equal force on the boy in the opposite direction . Since the boy is wearing roller skates, the opposite force exerted by the wall makes him backward, the boy on roller skates is exerting force on the wall towards the left side. The wall exerts an equal force on the boy towards the right side. Due to this, the boy moves in the backward direction. From this discussion, we conclude that when a boy exerts a force on the wall, the wall exerts an equal and opposite force on the boy . This is just an illustration of Newton’s third law of motion. Whenever one body exerts a force on another body, the second body exerts an equal and opposite force on the second body. The force exerted by the firs...
Read more

ELECTRIC CHARGES AND FIELDS , CLASS XII , MCQ Part 1

Image
           MULTIPLE CHOICE QUESTIONS   MCQ Questions for Class XII Physics electric charges and fields with Answers . Students can solve NCERT Class XII Physics electric charges and fields Latest Exam Pattern Multiple Choice Questions with Answers to know their preparation level. 1. An electric dipole placed in a non-uniform electric field will experience :                                    (a) Only a force (b) Only a torque (c) Both force and torque  (d) Neither force nor torque     Answer: d 2. Let N 1 be the number of electric field lines going out of an imaginary cube of side a that encloses an isolated point charge 2q and N 2 be the corresponding number for an imaginary sphere of radius a that encloses an isolated point charge 3q . Then (N 1 /N 2 ) is: (a) 1/ π (b) 2/3 (c) 9/4 (d) π Answer: b 3. A charge...
Read more