A machine takes in 500 J and delivers 350 J of useful output. Its efficiency is
Correct answer: C. 70%
- A. 30%
- B. 43%
- C. 70%
- D. 143%
Explanation
Efficiency is useful output divided by total input times 100, which is 350 over 500 times 100, giving 70%. The remaining 150 J is lost, mostly as heat through friction. An efficiency above 100% is impossible, so the last option can be discarded on principle alone.
Report an error
The more specific you are, the faster it gets fixed. A source beats an opinion.
Prefer email? support@testustad.com
About Energy Losses and Efficiency
Efficiency compares useful output energy or power with the total input, usually expressed as a percentage. The topic covers energy losses through friction, heating, resistance and sound, along with power ratings and Sankey diagrams. Efficiency is not the same as conservation of energy, because lost energy is transferred rather than destroyed.
Practise Work and Energy
748 free Work and Energy MCQs from Physics, each with the correct answer and an explanation. Unlimited attempts, no account needed.
Discussion
Stuck on an option, or know a faster way to get there? Ask or explain it here.
No comments yet. Be the first to explain this one.
Exams that ask Physics questions like this
Physics is on 16 papers prepared for on TestUstad, and all of them draw the same bank, so this question is worth knowing for every one of them.