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5 cards from this section. Quick, good the night before a test.
What is an energy audit?
Think of it as a check-up of energy use.
A 100 W bulb is switched on for 5 hours. How much energy does it use in kilowatt-hours?
Change watts to kilowatts by dividing by 1,000.
What does "1 unit" on an electricity bill mean?
The bill measures energy, not power.
A 40 W tube light is used for 10 hours. How much energy does it use?
Divide watt-hours by 1,000 to get kWh.
A classroom has 6 tube lights of 40 W and 4 fans of 75 W, all used for 6 hours on each of 200 school days, and electricity costs ₹8 per unit. Find the yearly energy use and cost. Then find the yearly saving if the tube lights are replaced by 20 W LED tubes and the fans are switched off during a one-hour break each day.
Work out each appliance group separately, then combine.
Explain why saving electricity in school helps the environment, and how adding rooftop solar panels would change where the school's electricity comes from.
Think about where grid electricity comes from and what a solar panel does.
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