Energy use in daily life Knowledge-Based Download PDF

Questions

1. 1.

   An electric lawnmower draws 1200 W of electrical power from the mains supply. If the lawnmower operates with an efficiency of 75%, at what rate is energy wasted to the surroundings as heat and sound?

   • A) 1600 W
   • B) 400 W
   • C) 900 W
   • D) 300 W
2. 2.

   A household replaces a traditional 100 W filament lamp with an energy-efficient 12 W LED lamp. If the lamp is switched on for an average of 5.0 hours per day, how much electrical energy is saved over a 30-day period?

   • A) 15.0 kWh
   • B) 13.2 kWh
   • C) 1.8 kWh
   • D) 0.44 kWh
3. 3.

   A domestic microwave oven operates with an efficiency of 60% and delivers 900 W of useful power to heat food. What is the total electrical power drawn by the microwave oven from the mains supply?

   • A) 1500 W
   • B) 540 W
   • C) 1440 W
   • D) 2250 W
4. 4.

   A rechargeable cordless vacuum cleaner has a battery that supplies 162 kJ of electrical energy. If the vacuum cleaner operates at a steady power rating of 180 W, for how many minutes can it run continuously before the battery is fully discharged?

   • A) 0.90 minutes
   • B) 9.0 minutes
   • C) 15 minutes
   • D) 25 minutes
5. 5.

   An electric kettle rated at 2.0 kW takes 150 seconds to boil water, transferring 240 kJ of thermal energy usefully to the water. How much energy is wasted to the surroundings during this process?

   • A) 540 kJ
   • B) 300 kJ
   • C) 160 kJ
   • D) 60 kJ
6. 6.

   An electric oven with a power rating of 3.0 kW is used continuously for 40 minutes. If the cost of electricity is 24 cents per kilowatt-hour (kWh), what is the total cost of running the oven for this period?

   • A) 16 cents
   • B) 32 cents
   • C) 48 cents
   • D) 72 cents
7. 7.

   An energy-efficient domestic LED lamp consumes 54 kJ of electrical energy when operated continuously for 1.5 hours. What is the power rating of the lamp?

   • A) 36 W
   • B) 600 W
   • C) 10 W
   • D) 15 W
8. 8.

   An electric food mixer draws 250 W of electrical power from the mains supply and dissipates 100 W to the surroundings as heat and sound. What is the efficiency of the food mixer?

   • A) 40%
   • B) 60%
   • C) 70%
   • D) 80%
9. 9.

   An electric hair dryer draws 1800 W of electrical power from a domestic supply and operates with an efficiency of 75%. How much energy is delivered as useful output during 2.0 minutes of continuous operation?

   • A) 54 kJ
   • B) 162 kJ
   • C) 216 kJ
   • D) 270 kJ
10. 10.

    An electric space heater with a power rating of 1500 W is operated for 4 hours each day. How much electrical energy, in kilowatt-hours (kWh), does the heater consume over a 30-day period?

    • A) 6 kWh
    • B) 45 kWh
    • C) 180 kWh
    • D) 180,000 kWh