CBSE Class 10 Science: Chapter 12 Electricity One-Shot Revision
Complete Chapter Summary, Mind Map, and Key Formulas
Welcome to Part 8, the final post in our 8-part series on Chapter 12, Electricity. This is your one-shot revision guide to quickly recap all the important concepts, formulas, and connections just before your exam. Let's get started!
Recommended Books for Deep Practice
Chapter at a Glance: Concept Mind Map
Electric Charge (Q)
SI Unit: Coulomb (C)
↓
Electric Current (I)
I = Q / t | SI Unit: Ampere (A)
↓
Potential Difference (V)
V = W / Q | SI Unit: Volt (V)
↓ (links Current & Voltage)
Ohm's Law
V = IR
↓ (defines)
Resistance (R)
R = ρL/A | SI Unit: Ohm (Ω)
↓ (leads to)
Resistors in Series
Rs = R₁ + R₂ + ...
(Current is same)
Resistors in Parallel
1/Rp = 1/R₁ + 1/R₂ + ...
(Voltage is same)
↓ (from Ohm's Law)
Electric Power (P)
P = VI = I²R = V²/R
↓ (leads to)
Heating Effect (Heat, H)
H = I²Rt
SI Unit: Joule (J)
Electrical Energy (E)
E = P × t
Commercial Unit: kWh
Quick Definitions: Key Terms
- Electric Current (I)
- The rate of flow of electric charge.
SI Unit: Ampere (A) - Potential Difference (V)
- Work done to move a unit charge from one point to another. (V = W/Q)
SI Unit: Volt (V) - Ohm's Law
- The potential difference across a conductor is directly proportional to the current flowing through it, at constant temperature. (V ∝ I)
- Resistance (R)
- The property of a conductor to oppose the flow of electric current. (R = V/I)
SI Unit: Ohm (Ω) - Resistivity (ρ)
- The resistance offered by a unit length and unit cross-sectional area of a material. It's a property of the material.
SI Unit: Ohm-meter (Ω·m) - Electric Power (P)
- The rate at which electrical energy is consumed. (P = VI)
SI Unit: Watt (W) - Joule's Law of Heating
- The heat produced in a resistor is given by H = I²Rt.
- Kilowatt-hour (kWh)
- The commercial unit of electrical energy.
1 kWh = 3.6 × 10⁶ J
Related Posts
Series vs. Parallel: At a Glance
| Parameter | Series Combination | Parallel Combination |
|---|---|---|
| Current (I) | Remains Same through each resistor. | Gets Divided among the resistors. (I = I₁ + I₂ + ...) |
| Voltage (V) | Gets Divided among the resistors. (V = V₁ + V₂ + ...) | Remains Same across each resistor. |
| Equivalent Resistance (Req) | Req = R₁ + R₂ + ... | 1/Req = 1/R₁ + 1/R₂ + ... |
| Total Resistance | Total resistance is greater than the largest individual resistance. | Total resistance is smaller than the smallest individual resistance. |
| Appliance Failure | If one fails, the circuit breaks and all stop working. | If one fails, the others continue to work. |
Top 5 Formulas to Memorize
- Ohm's Law: V = IR
- Resistance Factors: R = ρ (L / A)
- Series Combination: Rs = R₁ + R₂ + R₃
- Parallel Combination: 1/Rp = 1/R₁ + 1/R₂ + 1/R₃
- Power & Heat: P = VI, H = I²Rt, and E = P × t
Key Numerical Types to Practice
- Calculating total charge (Q=ne) or current (I=Q/t).
- Using Ohm's Law to find V, I, or R in a simple circuit.
- Calculating new resistance when a wire is stretched or its dimensions are changed (using R = ρL/A).
- Finding the equivalent resistance (Rs and Rp) for complex circuits (series-parallel combinations).
- Calculating heat produced using Joule's Law (H = I²Rt).
- Calculating the power (P = VI) of an appliance and the total energy consumed (E = P×t).
- Electricity Bill Problems: Converting energy to kWh and calculating the total cost.
Final Exam Tips
- Draw Diagrams: Always draw a simple circuit diagram for numericals. It helps you visualize the problem.
- Check SI Units: Ensure all values are in standard units (Amperes, Volts, Ohms, Meters, Seconds) before calculating.
- Series vs. Parallel: Memorize the rules! In **Series**, Current (I) is same. In **Parallel**, Voltage (V) is same.
- Heating Devices: Remember that all heating appliances (iron, toaster, fuse) work on the principle of **Joule's Law of Heating (H = I²Rt)**.
- Read Carefully: Pay attention to whether a wire is "cut" (area is constant) or "stretched" (volume is constant, so area changes).
- kWh Conversion: For billing problems, remember to convert Power (W) to Kilowatt (kW) by dividing by 1000, and Time (minutes) to Hours (h) by dividing by 60.
- Direction of Current: Always use the **conventional current** direction (positive to negative terminal) in your diagrams, even though electron flow is the opposite.
