CHAPTER -12 ELECTRICITY
GIST OF THE LESSON
- Positive and negative charges: The charge acquired by a glass rod when rubbed with silk is called positive charge and the charge acquired by an ebonite rod when rubbed with wool is called negative charge.
- Coulomb: It is the S.I. unit of charge. One coulomb is defined as that amount of charge which repels an equal and similar charge with a force of 9 x 109 N when placed in vacuum at a distance of 1 meter from it. Charge on an electron = -1.6 x 10-19 coulomb.
- Static and current electricities: Static electricity deals with the electric charges at rest while the current electricity deals with the electric charges in motion.
- Conductor: A substance which allows passage of electric charges through it easily is called a ‘conductor’. A conductor offers very low resistance to the flow of current. For example copper, silver, aluminium etc.
- Insulator: A substance that has infinitely high resistance does not allow electric current to flow through it. It is called an ‘insulator’. For example rubber, glass, plastic, ebonite etc.
- Electric current: The flow of electric charges across a cross-section of a conductor constitutes an electric current. It is defined as the rate of flow of the electric charge through any section of a conductor.
Electric current = Charge/Time or I = Q/t
Electric current is a scalar quantity.
- Ampere: It is the S.I. unit of current. If one coulomb of charge flows through any section of a conductor in one second, then current through it is said to be one ampere. 1 ampere = 1 coulomb/1 second or 1 A = 1C/1s = 1Cs-1 1 milliampere = 1 mA = 10-3 A 1 microampere = 1µA = 10-6 A
- Electric circuit: The closed path along which electric current flows is called an ‘electric circuit’.
- Conventional current: Conventionally, the direction of motion of positive charges is taken as the direction of current. The direction of conventional current is opposite to that of the negatively charged electrons.
- Electric field: It is the region around a charged body within which its influence can be experienced. Continue reading “Quick Revision for Class X Physics SA1”