Electricity

The flow of electric charge, typically through a conductor like copper wire.

  • Coulomb (symbol: C) is the unit used to measure electric charge in the International System of Units (SI). It describes the quantity of electric charge that is present or moved in a circuit.

  • A quantity of 1 C is equal to the electrical charge of approximately 6.24 x 1018 electrons or protons.

  • Current (I): Movement of electrons in a conductor, measured in Amperes (A).

    • Types of Current:

      • Direct Current (DC): Flows in one direction (e.g., batteries).

      • Alternating Current (AC): Reverses direction periodically (e.g., household electricity).

    • Current is like the flow of water in a pipe.

    • More current means a greater number of electrons flowing past a given point in a conductor per second.

    • current is not something that literally flows. Instead, it is a measure of the flow of charge at a specific point in the circuit. It exists at that point as the rate at which charge is passing through.

    • It's more accurate to say that current is a measure of how fast charge is flowing at a given location.

  • Voltage (V): Electrical potential difference between two points, measured in Volts (V). Voltage is the "pressure" that pushes electrons through a circuit.

    • Analogy: Voltage is like the water pressure in a pipe that pushes the water (electrons) through.

    • Example: A typical household battery may have a voltage of 1.5V, while wall outlets have 220V (or 110V, depending on the country).

  • Resistance (R): Opposition to the flow of current, measured in Ohms (Ω). Higher resistance means less current.

    • Factors Affecting Resistance:

      • Material: Conductors (e.g., copper) have low resistance, while insulators (e.g., rubber) have high resistance.

      • Length of the Conductor: Longer conductors have higher resistance.

      • Cross-sectional Area: Thicker wires have less resistance.

      • Temperature: As temperature increases, the resistance of most conductors increases.

    • Analogy: Resistance is like friction in a pipe that slows down the flow of water (current).

    • Example: A light bulb filament has high resistance, which limits the current and causes the filament to heat up and emit light.

  • Power (P): Rate at which electrical energy is converted into another form (e.g., heat, light), measured in Watts (W).

    • Formula: P = VI (Power = Voltage × Current)

2. Ohm’s Law

  • Ohm’s Law: Defines the relationship between voltage (V), current (I), and resistance (R).

    • Formula: V = IR (Voltage = Current × Resistance)

  • This helps in calculating any unknown quantity if the other two are known.

3. Electric Circuits

  • Series Circuit: Components are connected end-to-end.

    • Current: Same through all components.

    • Voltage: Sum of the voltage drops across each component equals the total supply voltage.

  • Parallel Circuit: Components are connected across the same two points.

    • Voltage: Same across all components.

    • Current: Sum of the currents through each component equals the total current from the power source.

AC vs. DC

  • DC (Direct Current): Used in batteries, solar panels, and small electronics.

  • AC (Alternating Current): Used in homes and businesses for powering large appliances because it is easy to transform to higher or lower voltages.