Question detail
A car engine converts chemical energy from petrol into useful mechanical work and also produces heat that is released into the surroundings. Identify one example of a useful energy transfer and one example of a wasted energy transfer in this process.
Try the question, check the answer, then read the explanation to understand the curriculum point.
At a glance
Question
Type
exam_style
Style
Topic
Conservation and dissipation of energy
Question
A car engine converts chemical energy from petrol into useful mechanical work and also produces heat that is released into the surroundings. Identify one example of a useful energy transfer and one example of a wasted energy transfer in this process.
Answer
The useful energy transfer is the conversion of chemical energy into mechanical work that moves the car. The wasted energy transfer is the heat released into the surroundings, which does not contribute to the car’s motion.
Explanation
The question tests the student’s ability to distinguish between useful and wasted energy transfers in a real device, directly addressing the learning objective of identifying useful and wasted energy transfers.
Common mistake
Confusing useful and wasted energy
Students often label all energy moving through a device as useful, ignoring energy lost as heat or friction.
Explain that useful energy is that which performs the intended work (e.g., mechanical work, light, sound), while wasted energy is energy that leaves the system in less useful forms such as heat, sound, or vibration, and is not used for the device’s purpose.
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