Types and purpose of household appliances
An appliance is a machine that does a job at home using electricity. We can group them by what they do with the energy:
- Heating: kettle, toaster, iron, hair dryer (also has a fan), electric stove, geyser. A heating wire turns electrical energy into heat.
- Motor: fan, mixer-grinder, washing machine, vacuum cleaner, hair dryer fan. A motor turns electrical energy into spinning motion.
- Cooling: refrigerator, air conditioner. A compressor moves heat from inside to outside.
- Light and electronics: LED bulb, TV, phone charger, computer.
By task: food (mixer, oven, kettle, fridge), hair and self-care (hair dryer, trimmer, straightener), clothes (iron, washing machine) and cleaning (vacuum cleaner, dishwasher).
Technical specs and working principles
Every appliance has a rating label. It tells you the supply voltage (for example 230 V), the power in watts (W) and sometimes the current in amperes (A) or the star rating for energy saving.
- Power P is how fast the appliance uses energy: P = V × I.
- Energy E = P × t. If P is in kW and t is in hours, E is in kilowatt-hours (kWh), also called one unit on the bill.
- Cost = units × price per unit.
Working principles in one line each: a heating element is a wire of high resistance that gets hot; a motor uses a magnet and a coil to spin; a fridge pumps heat out with a compressor; an LED gives light when current passes through a tiny semiconductor chip, using far less power than an old filament bulb.
Smart devices at home
A smart device has a small computer and a wireless link (usually Wi-Fi or Bluetooth). It can be controlled by a phone, a timer or a voice assistant.
- Smart plug: switches any plugged-in appliance on a schedule.
- Smart bulb and thermostat: change brightness or temperature to save energy.
- Self-care technology: smart watches count steps and heart rate, smart scales and trimmers keep records or adjust settings.
Benefits: convenience and saving energy. Limits: they use a little power all the time (standby), need a safe network and a strong password, and a smart plug has its own power limit.
Safe use and maintenance
- Never touch a plug or switch with wet hands. Water carries current.
- Use a plug and socket that match the appliance. Heavy appliances (geyser, AC, kettle, iron) need their own proper socket, not a thin extension board.
- Do not overload: add up the watts. A 6 A board at 230 V can give about 1380 W.
- Unplug before cleaning, and switch off a kettle or iron when you are done.
- Check cords for cuts and loose pins. Replace damaged wires, do not tape them.
- Keep vents of the fridge, TV and chargers clear so they do not overheat.
- Appliances with a metal body need the earth pin. Read the manual and ask an adult or an electrician for repairs.
Try it at home
With an adult, read the label of five appliances and write their watts. Estimate hours of use per day and work out the daily units. Which one uses the most?
Key formulas and definitions
- P = V × I (power = voltage × current)
- Energy (kWh) = power (kW) × time (h) = watts × hours ÷ 1000
- Cost = units × price per unit
- I = P ÷ V (current drawn by an appliance)
- 1 kWh = 1 unit = 3.6 million joules
Worked examples
1. A 9 W LED bulb is on for 5 hours every day. How many units does it use in 30 days?
Energy = 9 × 5 × 30 = 1350 Wh = 1.35 kWh = 1.35 units.
2. A 1200 W kettle runs for 10 minutes. How much energy does it use?
10 min = 1/6 hour. E = 1200 × 1/6 = 200 Wh = 0.2 kWh.
3. A 60 W fan runs 8 hours. If a unit costs ₹7, what is the cost?
E = 60 × 8 = 480 Wh = 0.48 kWh. Cost = 0.48 × 7 = ₹3.36.
4. A 1200 W kettle is used on 230 V. What current does it draw?
I = P ÷ V = 1200 ÷ 230 ≈ 5.2 A.
5. A 6 A extension board on 230 V supply has a kettle (1200 W) and a fridge (150 W). Is it safe?
Board limit = 6 × 230 = 1380 W. Load = 1200 + 150 = 1350 W, which is just under 1380 W. It works but with almost no margin. Better to plug the kettle in a separate wall socket.
6. An old 60 W bulb is replaced by a 9 W LED, used 5 hours a day for 30 days. How many units are saved, and how much money at ₹7 per unit?
Saving in power = 60 − 9 = 51 W. Energy = 51 × 5 × 30 = 7650 Wh = 7.65 kWh. Money = 7.65 × 7 = ₹53.55.
Common mistakes
- Mixing up watt (power) and watt-hour (energy). Power is how fast, energy is how much in total.
- Forgetting to divide by 1000 to change Wh into kWh.
- Thinking an appliance that is switched off at the remote uses no power. Standby still uses a little.
- Plugging a geyser, heater or iron into a thin extension board. These need a strong socket and thick wire.