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Physics · Class 10 · Chapter 16: Electricity
8 min
Key points
- Electric current is the flow of electric charges through a conductor — measured in Amperes
- Ohm's Law states that current through a conductor is directly proportional to voltage and inversely proportional to resistance
- Resistance is the opposition to the flow of electric current — measured in Ohms (Ω)
- Power is the rate of doing work or energy consumed per unit time — measured in Watts
- Electric energy is the work done by electric current — measured in Joules or kWh
- Series circuits have single path for current flow, parallel circuits have multiple paths
- In series connection, current remains same but voltage divides
- In parallel connection, voltage remains same but current divides
- WAPDA generates electricity at Tarbela Dam and supplies to cities like Karachi through transmission lines
Definitions
- Electric Current
- Electric current is the amount of charge flowing through any cross-section of a conductor in unit time. I = Q/t
- Potential Difference
- The potential difference between two points is the work done in moving unit positive charge from one point to another. V = W/Q
- Resistance
- Resistance is the property of a conductor which opposes the flow of current through it. R = V/I
- Electric Power
- Electric power is the rate at which electrical energy is consumed or converted into other forms of energy. P = VI
- Electromotive Force (EMF)
- EMF is the energy per unit charge supplied by a source like battery or generator. It is measured in volts.
Worked example
Define electric current and calculate the current flowing through a resistor of 10Ω when 5V potential difference is applied across it. (5 marks)
Electric current is the rate of flow of electric charge through a conductor. It is measured in amperes (A). Using Ohm's law: V = IR, where I = V/R. Given: V = 5V, R = 10Ω. Therefore: I = 5/10 = 0.5A
Common mistakes
- Students confuse series and parallel connections — remember series has one path, parallel has multiple paths
- Always write the formula before solving numerical problems
- Students forget to convert units (mA to A, kΩ to Ω) before calculations
- In parallel resistance formula, students forget to take reciprocal at the end
- Students mix up current and voltage behavior in series vs parallel circuits
Quick recap
Electric current is rate of flow of charge (I = Q/t). Potential difference is work done per unit charge (V = W/Q). Ohm's law states V = IR for constant temperature. Electric power P = VI and electric energy E = Pt. Series circuits have same current, parallel circuits have same voltage.
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