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Energy Transformations in Real-World Devices — Free MYP5 Physics Practice Questions
1QuestionIdentifying Input and Output Energy FormsConcept Practice
3 marks~5 minCriterion A
An electric car uses a lithium-ion battery pack and an electric motor to produce motion.
a
State the sequence of energy transformations that occurs from the stored energy in the battery to the movement of the car. [1]
b
Explain how the electric motor converts electrical energy into kinetic energy of the vehicle. [1]
c
Discuss one societal benefit and one societal limitation of widespread electric car adoption, referring to the energy transformations involved. [1]
Solutions
2QuestionDesigning Energy-Efficient SystemsAssessment Practice
2 marks~3 minCriterion C
An incandescent light bulb contains a thin tungsten filament. When the bulb is switched on, electrical current passes through the filament. The filament has a resistance of approximately 140 Ω at operating temperature, and the bulb is rated at 60 W.
a
Explain the primary energy transformation occurring in the filament. [1]
b
A student claims the bulb is an inefficient device because most input energy does not serve its intended purpose. Justify this claim using the concept of energy transformation. [1]
Solutions
3QuestionBattery to Mechanical Energy ConversionAssessment Practice
3 marks~5 minCriterion A
A toy car's electric motor converts electrical energy into kinetic energy. A student varies the battery voltage from 1.0 V to 3.0 V and records the car's speed, obtaining a straight-line graph through the origin: speed increases proportionally with voltage.
a
State the complete energy transformation sequence occurring in the motor as the car accelerates. [1]
b
Using and , explain why increasing the battery voltage causes greater current to flow and therefore greater power to be delivered to the motor. [1]
c
The graph is linear but does not pass through the origin in a real motor. Explain one reason why the car only begins moving above a threshold voltage. [1]
Solutions
4QuestionDesigning Energy-Efficient SystemsAssessment Practice
10 marks~15 minCriterion D
A school is replacing 200 incandescent bulbs (60 W each) with LED bulbs (9 W each). The school operates lighting for 8 hours per day, 200 days per year. Electricity costs 0.15 dollars per kWh. Each incandescent bulb lasts 1 000 hours; each LED lasts 25 000 hours. LED bulbs contain trace amounts of heavy metals including lead and arsenic.
a
State the annual energy saving, in kWh, achieved by replacing all 200 bulbs with LEDs. [2]
b
Analyse the economic case for the school investing in LED bulbs, using your answer to (a) and the lifespan data above. [4]
c
Evaluate the overall environmental impact of the school's switch to LED lighting. [4]
Solutions
5QuestionBattery to Mechanical Energy ConversionAssessment Practice
12 marks~18 minCriterion D
A company is developing an electric scooter powered by a lithium-ion battery. The company claims it is more environmentally friendly than a gasoline scooter. Both scooters travel 10 000 km per year for 5 years. The electric scooter uses 0.1 kWh per km and requires a new battery every 2 years; each battery requires 500 kWh to manufacture. The gasoline scooter uses 0.05 L per km, with a fuel energy density of 10 kWh per litre.
a
Describe one environmental impact of mining lithium or cobalt for batteries and explain how it harms the environment. [2]
b
Using the data above, calculate the total energy used by each scooter over 5 years, including battery manufacturing for the electric scooter. State which scooter uses less total energy. [4]
c
Evaluate the claim that the electric scooter is more environmentally friendly than the gasoline scooter. In your answer, identify one ethical concern related to battery material sourcing, suggest one company response, and justify whether the overall case for the electric scooter is convincing. [6]
Solutions
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