Electricity Practice

In parallel: (1) Each appliance gets the full supply voltage (230 V in India), so it operates at its rated power. (2) Each appliance can be switched on/off independently. (3) If one appliance fails, others continue to work. In series, voltage divides, appliances would not work at rated power, and failure of one breaks the whole circuit.

Electric power is the rate of doing work or converting energy: P = energy/time (unit: watt). Electrical energy is the total work done or energy converted in a given time: E = P × t (unit: joule or kWh). Power tells how fast; energy tells how much total.

A thicker wire has a larger cross-sectional area, giving lower resistance (R = ρl/A). Lower resistance means less energy is wasted as heat (H = I²Rt), and the wire can carry more current without overheating. That is why high-current circuits use thicker wires.

A short circuit occurs when the live and neutral wires (or two points in a circuit with very different potentials) are connected directly with negligible resistance — often due to damaged insulation. This causes a very large current to flow (I = V/R; R ≈ 0, so I → very large). The huge current can melt wires, cause fires, and damage appliances. Fuses and MCBs protect against short circuits.

A fuse is a thin wire with low melting point that melts and breaks the circuit when excess current flows — it is destroyed and must be replaced. An MCB (Miniature Circuit Breaker) is an automatic electromagnetic switch that trips and breaks the circuit when current exceeds the safe limit — it can be reset by flipping the switch back up. MCBs are more reliable, faster, and reusable; fuses are cheaper. Modern Indian homes increasingly use MCBs.

In metals, as temperature increases, the atoms vibrate with greater amplitude. This increases the frequency of collisions between free electrons (charge carriers) and the vibrating atoms, impeding the electron flow more. More collisions mean more opposition to current — higher resistance.