28/12/2025
CURRENT ELECTRICITY
(Class 10.ICSE/CBSE)
Current electricity covers fundamental concepts like electric current, potential difference, resistance, and their applications in circuits, essential for CBSE, ICSE, and WBBSE Class 10 syllabi. These notes provide key definitions, formulas, and explanations aligned with Indian school curricula.
Key Definitions
Electric current (I) is the flow of electric charge through a conductor per unit time, with formula I = Q/t and unit ampere (A), where 1 A means 1 coulomb flows per second.
Potential difference (V) is the work done per unit charge to move it between two points, given by V = W/Q, with unit volt (V), where 1 V equals 1 joule per coulomb.
Resistance (R) opposes current flow, calculated as R = V/I, measured in ohms (Ω); it depends on length (R ∝ L), cross-sectional area (R ∝ 1/A), material nature, and temperature.
Ohm's LawOhm's Law states that current through a conductor is directly proportional to potential difference across its ends at constant temperature, expressed as V = IR, with a straight-line V-I graph for ohmic conductors.
Resistivity (ρ) is resistance of unit length and unit area material, formula R = ρL/A, unit ohm-metre (Ω·m), depending only on material.
Resistor CombinationsIn series, total resistance Req = R1 + R2 + ..., with same current but voltage dividing across resistors.
In parallel, 1/Req = 1/R1 + 1/R2 + ..., with same voltage but current dividing.
Power and HeatingElectric power P = VI = I²R = V²/R, unit watt (W), where 1 W is 1 ampere at 1 volt.
Heating effect follows Joule's Law: heat H = I²Rt; used in heaters, fuses (low-melting wire breaks circuit on overload).
Electrical energy = power × time, commercial unit kWh (1 kWh = 3.6 × 10⁶ J).
