CBSE Class 10 Physics Electricity (1). Learning the important concepts is very important for every student to get better marks in examinations. The concepts should be clear which will help in faster learning. The attached concepts made as per NCERT and CBSE pattern will help the student to understand the chapter and score better marks in the examinations.
Electricity is a general term that encompasses a variety of phenomena resulting from the presence and flow of electric charge. These include many easily recognizable phenomena such as lightning and static electricity, but in addition, less familiar concepts such as the electromagnetic field and electromagnetic induction.
Electric charge is a fundamental conserved property of some subatomic particles, which determines their electromagnetic interaction. Electrically charged matter is influenced by, and produces, electromagnetic fields. The interaction between a moving charge and an electromagnetic field is the source of the electromagnetic force, which is one of the four fundamental forces. Electric charge is conserved, additive and quantised.
The S.I. unit of electric charge is ‘C’ coulomb. Any other charged body will have a charge Q
Q = ne
where n is the number of electrons and e is the charge on electron = 1.6 x 10–19 coulombs.
Electric current is a flow of electrons in a conductor such as a metal wire. Electric current is expressed by the amount of charge flowing through a particular area in unit time. In other words, it is the rate of flow of electric charges. In circuits using metallic wires, electrons constitute the flow of charges. However, electrons were not known at the time when the phenomenon of electricity was first observed. So, electric current was considered to be the flow of positive charges and the direction of flow of positive charges was taken to be the direction of electric current. 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. The magnitude of electric current in a conductor is the amount of electric charge passing through a given point of conductor in 1 second.
I = Q/t
S.I. unit of electric current is ‘A’ (Ampere).
The electric current is expressed by a unit called ampere (A), named after the French scientist,
Andre-Marie Ampere (1775–1836).
When 1 coulomb of charge flows through any cross-section of a conductor in 1 second, the
electric charge flowing through it is said to be 1 ampere.
Smaller unit current is milliampere(mA) and microampere(m A)
1 mA = 10–3A
1 m A = 10–6A
An instrument called ammeter measures electric current in a circuit. It is always connected in series in a circuit through which the current is to be measured. The direction of electric current is from positive terminal to negative terminal through the electric circuit.
INTEXT QUESTIONS PAGE NO. 200
1. What does an electric circuit mean?
Ans. An electric circuit consists of electric devices, switching devices, source of electricity, etc. that are connected by conducting wires.
2. Define the unit of current.
Ans. The unit of electric current is ampere (A). 1 A is defined as the flow of 1 C of charge through a wire in 1 s.
3. Calculate the number of electrons constituting one coulomb of charge.
Ans. One electron possesses a charge of 1.6 × 10−19 C, i.e., 1.6 × 10−19 C of charge is contained in 1 electron.
∴ 1 C of charge is contained in 1/1.6 × 10−19 =1 6.25×1018 electrons
Therefore, 6.25´1018 electrons constitute one coulomb of charge.
Potential difference, VA – VB between two points A and B is the work done per unit charge in taking a charge from B to A.
Potential difference, VA – VB =work done/charge
, where VA is potential at point A, VB is potential
at point B and S.I. unit of potential is volts (V), named after Alessandro Volta (1745–1827), an Italian physicist.
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