Topic 1Electric Current
Electric Current = conductor में electrons के flow की rate। Symbol = I।
⚡
I = q/t | S.I. Unit = Ampere (A) | Measured by: Ammeter
I = q / tCurrent = Charge/Time
q = I × tCharge = Current × Time
q = n × en=electrons, e=1.6×10⁻¹⁹ C
- 🔸 q = Total charge (Coulombs)
- 🔸 n = Number of electrons
- 🔸 e = Charge of 1 electron = 1.6 × 10⁻¹⁹ C
- 🔸 1 Coulomb = 6.25 × 10¹⁸ electrons ≈ 6 × 10¹⁸ e⁻
Topic 2Conductor
🔌
Conductor = वो material जो electric charge (current) को एक या ज़्यादा directions में flow करने देता है।
🥇
Best conductors: Silver > Copper > Gold > Aluminium — इनकी resistivity सबसे कम होती है।
Topic 3Potential Difference (Voltage)
Potential Difference = electric field में एक point से दूसरे point तक unit positive charge move करने में किया गया work।
🔋
V = W/Q | S.I. Unit = Volt (V) | Measured by: Voltmeter
V = W / QVoltage = Work/Charge
W = qVWork = Charge × Voltage
1 Volt = 1 J/C1 Joule per Coulomb
💡
1 Volt = वो energy जो एक unit charge को एक point से दूसरे point तक move करने के लिए चाहिए।
Topic 4Ohm's Law
📜
Ohm's Law: "Conductor में flow होने वाला current, conductor के across voltage के directly proportional होता है — provided temperature और physical conditions constant रहें।"
📅
दिया: George Simon Ohm ने 1827 में।
V = I × RVoltage = Current × Resistance
I = V / RCurrent = Voltage/Resistance
R = V / IResistance = Voltage/Current
📈
V-I Graph: Slope जितना steep → Resistance उतनी ज़्यादा। V ∝ I — Straight line graph।
Topic 5Resistance & Resistivity
🔩 Resistance (R)
Resistance = किसी electrical component की property जो electric current के flow को resist करे।
Ω
S.I. Unit = Ohm (Ω) | Formula: R = ρL/A
- 🔸 R = Resistance
- 🔸 ρ = Resistivity of material
- 🔸 L = Length of conductor
- 🔸 A = Area of cross-section
📊 Resistivity (ρ) / Specific Resistance
Resistivity = material की वो measure जो बताए कि वो electrical current के flow को कितनी strongly oppose करता है। Resistivity constant होती है।
ρ = Ω × mS.I. Unit of Resistivity
R = ρL/AResistance Formula
Topic 6Factors Affecting Resistance
📏
Length (L)
Resistance, length के directly proportional होती है।
R ∝ L
⭕
Area of Cross-Section (A)
Resistance, area के inversely proportional। Thicker wire = कम resistance।
R ∝ 1/A
🌡️
Temperature (T)
Metals में: R बढ़ती है। Semiconductors में: R घटती है।
R ∝ T (metals)
🧱
Nature of Material (ρ)
कम resistivity → better conductor। ज़्यादा resistivity → insulator।
R = ρL/A
💡
Metals में temperature बढ़ने पर atoms ज़्यादा vibrate करते हैं → electrons से collisions बढ़ती हैं → resistance बढ़ती है।
Semiconductors में उल्टा होता है।
Semiconductors में उल्टा होता है।
Topic 7Conductance
Conductance = measure of how easily electricity flows through a component। Resistance का inverse होता है।
📡
Symbol: G | G = 1/R | S.I. Unit = Siemens (S)
Topic 8Conductors, Semiconductors & Insulators
✅ Conductors
High electrical conductivity, low resistivity। Current easily flow होती है।
Examples: Copper, Silver, Gold, Aluminium, Steel
Examples: Copper, Silver, Gold, Aluminium, Steel
🔵 Semiconductors
Conductivity, conductors और insulators के बीच होती है। Controllable conductivity।
Examples: Silicon (Si), Germanium (Ge), Arsenide compounds
Examples: Silicon (Si), Germanium (Ge), Arsenide compounds
❌ Insulators
High resistivity, low conductivity। Current flow नहीं होती।
Examples: Rubber, Glass, Plastic, Air, Pure water
Examples: Rubber, Glass, Plastic, Air, Pure water
Topic 9Resistivity Table
| Category | Material | Resistivity (Ω·m) |
|---|---|---|
| ✅ Conductors | ||
| Silver | 1.60 × 10⁻⁸ | |
| Copper | 1.62 × 10⁻⁸ | |
| Aluminium | 2.63 × 10⁻⁸ | |
| Tungsten | 5.20 × 10⁻⁸ | |
| Nickel | 6.84 × 10⁻⁸ | |
| Iron | 10.0 × 10⁻⁸ | |
| Chromium | 12.9 × 10⁻⁸ | |
| Mercury | 94.0 × 10⁻⁸ | |
| Manganese | 1.84 × 10⁻⁶ | |
| 🔀 Alloys | ||
| Constantan (Cu + Ni) | 49 × 10⁻⁶ | |
| Manganin (Cu + Mn + Ni) | 44 × 10⁻⁶ | |
| Nichrome (Ni + Cr + Mn + Fe) | 100 × 10⁻⁶ | |
| ❌ Insulators | ||
| Glass | 10¹⁰ – 10¹⁴ | |
| Hard Rubber | 10¹³ – 10¹⁶ | |
| Ebonite | 10¹⁵ – 10¹⁷ | |
| Diamond | 10¹² – 10¹³ | |
| Paper (dry) | 10¹² | |
Topic 10Resistance Combination — Series & Parallel
🔗 Series Connection
- Resistors end-to-end connected होते हैं
- Current (I) = सभी में same
- Voltage (V) = divide होती है
- Req = R1 + R2 + R3 + … + Rn
- Total resistance = sum of all
⚡ Parallel Connection
- Resistors same 2 points पर connected
- Voltage (V) = सभी में same
- Current (I) = divide होता है
- 1/Req = 1/R1 + 1/R2 + 1/R3 + … + 1/Rn
- Total resistance = always कम होती है
R_series = R1+R2+…+RnSeries Formula
1/R_parallel = 1/R1+1/R2+…Parallel Formula
🏠
घर में circuits Parallel में होते हैं — हर appliance को same voltage मिले और एक बंद हो तो दूसरे चलते रहें।
Topic 11Heating Effect of Electric Current
जब electric current conductor में flow करे → conductor की resistance की वजह से heat produce होती है — यही Heating Effect है।
🔥
Joule's Law of Heating: H = I²Rt | H = VIt | H = V²t/R
H = I²RtJoule's Law
H = VItUsing V = IR
H = V²t/RAlternate form
- 🔸 H = Heat energy (Joules)
- 🔸 I = Current (Amperes)
- 🔸 R = Resistance (Ohms)
- 🔸 t = Time (Seconds)
Topic 12Applications of Heating Effect
| Application | Details |
|---|---|
| ⚡ Electric Heater | Nichrome wire heating element के रूप में use होती है |
| 💡 Electric Bulb | Tungsten filament — high melting point की वजह से use होता है |
| 👕 Electric Iron | Heating effect से कपड़े iron होते हैं |
| 🔌 Fuse | Low melting point wire — excessive current पर melt होकर circuit break करती है |
📌
Nichrome क्यों use होती है heating devices में? — High resistance है + High temperatures पर easily oxidize नहीं होती!
🔌
Fuse = जब excessive current flow हो → fuse wire melt होती है → circuit break → appliances protect होते हैं। Short circuit और mismatched loads से protection।
🔁 Open और Closed Circuit
🟢 Closed Circuit
- Switch ON होती है
- Complete path बनती है
- Current flow होती है
- Lamp जलती है
🔴 Open Circuit
- Switch OFF होती है
- Path break होती है
- Current flow नहीं होती
- Lamp नहीं जलती
Topic 13Electric Power
Electric Power = वो rate जिस पर electrical energy consume या produce होती है।
⚡
P = VI | P = I²R | P = V²/R | S.I. Unit = Watt (W)
P = VIPower = Voltage × Current
P = I²RUsing V = IR
P = V²/RAlternate form
Topic 14Commercial Unit of Energy — kWh
💡
1 unit = 1 kWh — यही electricity bill में count होती है!
- 🔸 1 kWh = 1 kW × 1 hour
- 🔸 = 1000 Watts × 3600 seconds
- 🔸 = 3,600,000 Joules
- 🔸 = 36 × 10⁵ Joules
- 🔸 = 3.6 × 10⁶ J
1 kWh = 3.6×10⁶ JCommercial Unit Conversion
Topic 15Colour Coding in Household Wiring
🔴
Live Wire (Phase Wire)
Color: Red | High Voltage | ⚡ Dangerous
⚫
Neutral Wire
Color: Black | Voltage = 0 | Return path
🟢
Earth Wire (Ground Wire)
Color: Green/Yellow | Safety wire | Thick बनाई जाती है ताकि higher currents handle हो
📋
Appliance Standard: 220V, 50Hz — India में household current यही है।
🔌
Earth wire को thick बनाया जाता है ताकि वो higher currents को low resistance के साथ manage कर सके।
Topic 16Wheatstone Bridge
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Wheatstone Bridge: Unknown resistance accurately measure करने के लिए एक electrical circuit — 4 resistors का bridge circuit बनाकर balance होता है।
P/R = Q/SWheatstone Bridge Formula
⚖️
जब bridge balanced हो (galvanometer में zero current) → P/R = Q/S। इससे unknown resistance S = QR/P calculate होती है।
Topic 17Kirchhoff's Laws
⚡ KCL — Law of Current (Junction Rule)
किसी circuit में एक node (junction) में enter होने वाला total current = उस node से leave होने वाले total current के equal।
ΣI_in = ΣI_outKirchhoff's Current Law
💡
Based on: Conservation of Charge — charge न create होती है, न destroy।
🔋 KVL — Law of Voltage (Loop Rule)
किसी closed loop में सभी voltages (EMFs और voltage drops) का sum = zero।
ΣV = 0Kirchhoff's Voltage Law
💡
Based on: Conservation of Energy — energy न create होती है, न destroy।
Quick RevisionAll Key Formulas at a Glance
I = q/tElectric Current
V = W/QPotential Difference
V = IROhm's Law
R = ρL/AResistance
R_s = R1+R2+…Series Resistance
1/R_p = 1/R1+…Parallel Resistance
H = I²RtJoule's Heating Law
P = VI = I²RElectric Power
1 kWh = 3.6×10⁶ JCommercial Energy Unit
P/R = Q/SWheatstone Bridge
ΣI_in = ΣI_outKCL
ΣV = 0KVL
🧠
Wire Colors Trick: 🔴 Red = Live (ख़तरनाक) | ⚫ Black = Neutral (safe) | 🟢 Green = Earth (safety wire)
Nichrome = Heating · Tungsten = Bulb · Fuse = Low melting point
Nichrome = Heating · Tungsten = Bulb · Fuse = Low melting point