PHYSICS CONNECTION
Mechanical and electrical power measure the same rate
A motor transfers electrical energy into mechanical work and other forms. Comparing input and useful output powers gives efficiency.
Pin = VI Puseful = Fv Efficiency = Puseful/Pin
Follow the reasoning
- Calculate the electrical input power.
- Calculate the useful mechanical output power.
- Compare them and account for the remaining transfer rate.
OFFICIAL OCR QUESTIONS
Try it in a past paper 1
Open the question, then use its mark scheme to check your work.
Question 2
Design and analyse an experiment comparing a lifting motor’s electrical input with its useful mechanical output.
A curated collection checked against the question papers and mark schemes; not a complete past-paper catalogue. Links open official OCR PDFs in a new tab.
ORIGINAL PHYSICSUK QUESTIONS
Put the ideas to work
More practice is on its way
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Specification outcomes (5)
- 3.3.3(a) Define power, the unit watt, and use P = W / t.
- 3.3.3(b) Use and derive P = Fv from first principles.
- 3.3.3(c) Calculate efficiency of a mechanical system using percentage efficiency = (useful output energy / total input energy) × 100.
- 4.2.5(a) Use and apply power equations P = IV, P = I²R, and P = V² / R.
- 4.2.5(b) Use energy transfer equation W = VIt.