Electricity Handwritten Notes PDF

# Electricity ## Charge (Q): - Two types of charge: + and - - SI unit of charge: Coulomb (C) - Smallest independent charge: electron (e) (1e = 1.6 x 10⁻¹⁹ fundamental charge) ## Current (I): - Current is the rate of flow of charge. - Flow of +ve charge - Direction of current: opposite to fl...

# Electricity ## Charge (Q): - Two types of charge: + and - - SI unit of charge: Coulomb (C) - Smallest independent charge: electron (e) (1e = 1.6 x 10⁻¹⁹ fundamental charge) ## Current (I): - Current is the rate of flow of charge. - Flow of +ve charge - Direction of current: opposite to flow of e⁻ - SI unit of current: Ampere (A) - Formula: I = Q/t - Q = It - 1A = 10³ mA = 10⁶ μA ## Potential Difference (PD) (V): - Potential difference between two points is the amount of work done in moving a unit charge (1C) from one point to the other. - Formula: V = W/Q - W = QV - Potential difference is measured by a Voltmeter. - Electric current (A) is measured by an Ammeter. - Current ka PAPA --> Potential Difference (V) [PD]: - Electron flows from lower potential to higher potential. - I flows from higher potential to lower potential. ## Resistance (R): - Obstruction offered to the flow of charges (current). - Property of a conductor to obstruct the flow of charges. - Formula: Q = It - W = QV ## Factors on Which Resistance of (Conductor) Depends: - Length(l) - Formula: R α l - Area of cross-section (A) - Formula: R α 1/A - Material: resistivity (P) - Resistivity property of material - Temperature: Temperature ↑ - Formula: R = (P*l)/A - SI unit of R: Ohm (Ω) - SI unit of p = Ωm - Formula: R = (P*l)/A - P = RA - A = πr² - diameter (d) = 2r - r = d/2 - d (mm) = 10⁻³m - cm = 10⁻²m ## Resistivity (P): - P is a property of the material. - Metals and alloys have low p (10⁻⁸ Ωm to 10⁻⁶ Ωm). - Good conductor of electricity. - Copper and aluminium are used for transmission lines. - Insulators like rubber and glass have high p (10² Ωm to 10¹⁰ Ωm). ## Ohm’s Law: - The potential difference, V, across the ends of a metallic conductor is directly proportional to the current flowing through it provided its temperature remains the same. - Trick: VIRal - Formula: V = IR - V α I - Temp = const ## Ohm's Law and Experimental Setup: - Formula: V = IR - I - V st line pass origin - Slope ↑ = RT ## Combination of Resistors: - **Series:** - I → Same - V → Different - Trick: YIRal - Formula: Y = IR - Formula: Re = R₁ + R₂ + R₃ - **Parallel** - I → Different - V → Same - Formula: 1/Re = 1/R₁ + 1/R₂ +1/R₃ - Formula: Re = (R₁ x R₂)/(R₁ + R₂) - Formula: Rp < Rs ## Disadvantage of Series Combination: - If one device fails, all other devices in that series will not work. - e.g., Diwali ki lights. - Devices of different types need different current, for e.g., a bulb and heater needs different current and cannot be connected in series. This can be done with parallel combinations. ## Circuit Diagram - **Circuit** - Continuous and closed path of electric current. - **Electric Bulb:** - Symbol: () - **A Resistor of Resistance R:** - Symbol: --- --- - **Variable Resistance or Rheostat:** - Symbol: --- --- - **Ammeter:** - Symbol: A - **Voltmeter:** - Symbol: V ## Electric Power: - **Rate at which Electrical Energy is consumed.** - Trick: Paya! P = VI - Formula P = VI - P = i²R - P = V²/R ## Electrical Energy (E): - Supplied by cell - SI Unit: Joule - Formula: E = P x t - 1 kWh = 3.6 x 10⁵ J ## Bijli ka Bill Banao: - Energy ka Paisa - Electric meter → 1 unit of energy - 1 unit = 1 kWh - Formula: Bill = no. of units x price of unit ## Heating Effect of Electric Current: - When an electric current passes through a conductor or an electric device, the conductor becomes hot after some time and produce heat. This is called heating effect or electric current. - e.g. Bulb, Fan, Toaster, Mobile Phone ## Joule’s Law of Heating: - Heat produces in a resister. - SI unit: J - Formula: H = i²Rt - Formula: H = (V²t) / R - Practical application of heating effect of electric current: - High resistivity → Heat ↑ - High melting point - Alloys: - Do not oxide ## Electric Bulb: - Filament: Tungsten (High melting point). Filament is heated and it emits light. - Most of energy consumed appears as heat, only a small part as heat. - Only a small part as light. - Tungsten has a very high melting point ## Electric Fuse - Safety Device: - Electrical fuse used to prevent short circuit. Fuse has low melting point so when a high current passes through it melts and stops the flow of current. - Formula: H = i²Rt - Fuse wire in series with the appliance. - Fuse wire: Alloy of Al, Cu, lead, Iron ## Fuse Wire Should Have: - High resistivity → Resistance ↑ → Heat ↑ → Temp ↑ → melt - Low melting point. - If high current flows (more than required) fuse wire gets heated up and melts - Rating of fuse: 1A, 2A, 3A, 4A, 5A, 10A, etc. - Rating of fuse wire → Max current ## Define SI Unit of Current 1 Ampere: - Formula: Q = It , then I = Q/t - I = 1A = 1C/1S - If one coulomb of charge flows through a conductor in one second, the current flowing through the conductor is known as one ampere ## Define SI unit of Potential Difference 1 Volt: - Formula: W = QV, then V = W/Q - V = 1J/1C = 1V - The potential difference between two points is said to be 1 volt if 1 joule of work is done in moving a positive change of 1 coulomb from one point to the other. ## Define SI unit of Resistance 1 Ohm: - Formula: V = IR then R = V/I - R = 1V/1A = 1Ω - One ohm is defined as the resistance of an object when a current of 1 ampere flows through an object on applying potential difference of 1V. ## Define SI unit of Power 1 Watt: - Formula: P = Vi - Formula: 1W = 1V x 1A - 1 Watt is the Power consumed in a circuit when 1 ampere of current flows on applying a potential difference 1 volt.