CBSE Class 10 - Physics - Electricity - Important Points To Remember (#cbsenotes)

Electricity - Important Points To Remember 

CBSE Class 10 - Physics 

① Electric current is defined as the amount of charge flowing through a particular cross section area in a unit time.


② The SI unit of electric current is ampere.


③ A stream of electrons moving through a conductor constitutes an electric current. In a conventional current, the direction of current is taken opposite to the direction of flow of electrons i.e. flow of positive charges from +ve terminal to -ve terminal.


④ 1 A is the flow of 6.25 × 10¹⁸ electrons per second, or 1 coulomb per second.




⑤ Electric potential difference between points in an electric circuit is the work done to move a unit positive charge from one point to another.


⑥ The difference in electric potential between two points is called potential difference. It is measured in volts (V).


⑦ To set the electrons in motion in an electric circuit, we use a cell or a battery. A cell generates a potential difference across its terminals.


⑧ A multi-meter is an electronic measuring instrument that combines several measuring functions (electric potential difference, electric current and electric resistance) in one unit.


⑨ 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.


⑩ The voltmeter is always connected in parallel across the points between which the potential difference is to be measured.


⑪ An instrument used to detect presence and direction of current flowing is called a galvanometer.


⑫ The property of a material that resists electric current, is called resistance and it measured in ohms (Ω). Resistance is the opposition that a substance offers to the motion of electrons.


⑬ Ohms law: The current through a conductor element is proportional to the potential difference applied between its ends, provided the temperature remains constant. Mathematically V=IR.


⑭ Ohm’s law is valid for metal conductors at constant temperature. It is not applicable for gaseous
conductors and semiconductors.


⑮ Resistance of a wire depends on the material of the wire, its length and its area of cross section R α l/A.


⑯ A potential difference of 1 V across a resistance of 1 Ω produces a current of 1 A.


⑰ The equivalent resistance of several resistors in series is equal to the sum of their individual resistances.


⑱ A set of resistors connected in parallel has an equivalent resistance Rₚ given by
1/Rₚ = 1/R₁ + 1/R₂ + 1/R₃ + ...

⑲ The electrical energy dissipated in a resistor is given by W = V × I × t


⑳ The unit of power is watt (W). One watt of power is consumed when 1 A of current flows at a potential difference of 1 V.

21 Electrical energy is the product of power and time. Units of electrical energy W-s and KWH.

22 The commercial unit of electrical energy is kilowatt hour (kWh).
       1 kW h = 3,600,000 J = 3.6 × 10 6 J.