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Electricity

What will you learn

  • A stream of electrons moving through a conductor constitutes an electric current.

  • Conventionally, the direction of current is taken opposite to the direction of flow of electrons.

  • The SI unit of electric current is ampere.

  • To set the electrons in motion in an electric circuit, we use a cell or a battery. A cell generates a potential difference across its terminals. It is measured in volts (V).

  • Resistance is a property that resists the flow of electrons in a conductor. It controls the magnitude of the current. The SI unit of resistance is ohm (Ω).

  • Ohm’s law: The potential difference across the ends of a resistor is directly proportional to the current through it, provided its temperature remains the same.

  • The resistance of a conductor depends directly on its length, inversely on its area of cross-section, and also on the material of the conductor.

  • The equivalent resistance of several resistors in series is equal to the sum of their individual resistances.

  • The electrical energy dissipated in a resistor is given by W = V × I × t

  • The unit of power is watt (W). One watt of power is consumed when 1 A of current flows at a potential difference of 1 V.

  • The commercial unit of electrical energy is kilowatt hour (kWh).

  • 1 kW h = 3,600,000 J = 3.6 × 106 J.