Flashcards
UNIT 1.2.1 - UNDERPINNING ENERGY CONCEPTS
Cards in this deck (9)
- 1Energy can never be __________ or __________, it can only be ______________ from one _____ to another.Energy can never be CREATED or DESTROYED,
it can only be TRANSFERRED from one FORM to another.
- 2Energy can only be used when it is transferred from one form to another. This is called ______.Energy can only be used when it is transferred from one form to another.
This is called WORK.
- 3When work is done some of the energy is transferred into __________ forms, while some of the energy will be transferred into _________ forms.When work is done some of the energy is transferred into USEFUL forms, while some of the energy will be transferred into WASTE forms.
- 4—
- 5—
- 6A light bulb is supplied with a total of 150J of electrical energy. The bulb gives off 60J of light energy. Calculate the percentage efficiency of the bulb using the equation:Percentage efficiency = (60 ÷ 150) x 100
Percentage efficiency = 40%
- 7How much energy does a 150W light bulb transfer in: a) three seconds b) one minuteThe POWER of an electrical appliance tells us how much electricity it transfers in one second.
Power is measured in Watts (W).
1 Watt = 1 Joule of electrical energy transferred per second. 1 W = 1 J/s
a) energy transfer = power x time
energy transfer = 150 x 3
energy transfer = 450J
b) a) energy transfer = power x time
energy transfer = 150 x 60
energy transfer = 9,000J
- 8A 2,500 W electric heater is switched on for 4 hours. Calculate the energy used in that time and the cost of using the appliance if 1 unit costs 9 pence.E = P × t where:
E is the energy transferred in kilowatt hours, kWh
P is the power in kW
t is the time in hours.
Power = 2,500 W = 2.5 kW
Energy used = 2.5 × 4 = 10 kWh
Cost = 10 × 9 = 90 pence
- 9A 200W TV is used for an average of 3 hours each day. Calculate how much the TV costs to run per week. Cost of 1 unit = 10 pence.E = P × t where:
E is the energy transferred in kilowatt hours, kWh
P is the power in kW
t is the time in hours.
Power = 200W = 0.2kW
Energy used = 0.2 × (3 x 7) = 4.2 kWh
Cost = 4.2 × 10 = 42 pence
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- Year 11 Physics Flashcards on UNIT 1.2.1 - UNDERPINNING ENERGY CONCEPTS, created by Mr S Lee on 29/03/2018.
- Created by
- Mr S Lee · Mar 2018
- Updated
- May 17, 2018
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