⚡ Introduction

Electricity is an essential part of our daily life. This chapter covers electric current, potential difference, Ohm’s law, resistance, factors affecting resistance, series and parallel combinations, and electrical energy and power.

๐Ÿ”Œ 1. Electric Current and Circuit

Electric Current (I): Flow of electric charge. It is defined as: Where:

  • I = current (ampere)

  • Q = charge (coulomb)

  • t = time (seconds)

Electric Circuit: A closed path in which current flows.

Direction of Current: Conventional current flows from positive to negative terminal.

๐Ÿ”‹ 2. Potential Difference

Potential Difference (V): Work done to move a unit charge between two points. Where:

  • V = potential difference (volts)

  • W = work done (joules)

  • Q = charge (coulomb)

Measured by a voltmeter connected in parallel.

๐Ÿ”ง 3. Ohm’s Law

Ohm’s law states that: Where:

  • V = potential difference

  • I = current

  • R = resistance (ohm)

Resistance (R): Opposition to the flow of current.

Graph of V vs I is a straight line for an ohmic conductor.

๐Ÿงฒ 4. Resistance and Factors Affecting It

Factors affecting resistance: Where:

  • R = resistance

  • = resistivity

  • l = length of conductor

  • A = cross-sectional area

  • Resistance ∝ length (l)

  • Resistance ∝ 1/area (A)

  • Depends on the material (resistivity)

๐Ÿ”— 5. Resistors in Series and Parallel

Series Combination:

  • Total resistance:

  • Current same in all resistors

  • Voltage divides

Parallel Combination:

  • Voltage same across each resistor

  • Current divides

Which is better? Parallel is preferred in household wiring due to constant voltage.

๐Ÿ’ก 6. Heating Effect of Electric Current

When current flows through a resistor, it produces heat. Where:

  • H = heat produced (Joules)

  • I = current

  • R = resistance

  • t = time

Applications:

  • Electric heater, toaster, iron

  • Electric bulb, fuse

⚙️ 7. Electric Power

Electric Power (P): Rate at which electric energy is consumed.

Unit: Watt (W)

  • 1 kilowatt (kW) = 1000 W

Electrical Energy:

  • Unit: kilowatt-hour (kWh)

✅ Key Points to Remember

  • Current is the flow of charges; measured in ampere.

  • Ohm’s law defines the relation between V, I, and R.

  • Series: current same; Parallel: voltage same.

  • Heat is produced when current flows through a resistor.

  • Power = VI, Energy = Pt