National 5PhysicsSQARevision NotesElectricityElectrical PowerElectrical Energy & Electrical Power

Electrical Energy & Electrical Power (SQA National 5 Physics): Revision Note

Exam code: X857 75

Katie M

Written by: Katie M

Reviewed by: Caroline Carroll

Updated on

Electrical energy & electrical power

  • Power is defined as 

The amount of energy transferred per unit of time

  • Power can be calculated using 

P space equals space E over t

  • Where:

    • P = power, measured in watts (W)

      • 1 space straight W space equals space 1 space straight J space straight s to the power of negative 1 end exponent

    • E = energy transferred, measured in joules (J)

    • t = time, measured in seconds (s)

Relationship triangle for energy, power, and time

Energy Power Time Triangle

Cover up the variable you need to calculate, and the triangle shows you how the equation is arranged

  • Using relationship triangles is covered in more detail in the revision note on motion relationships

  • Consider two electric motors lifting the same weight through the same height

    • The motor that lifts the weight faster has greater power

Two motors with different amounts of power

Electric Motors Power, downloadable AS & A Level Physics revision notes

The motor with the most power lifts the weight faster for a given height

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    Author
    Reviewer
    Katie M

    Author: Katie M

    Expertise: Physics Content Creator

    Katie has always been passionate about the sciences, and completed a degree in Astrophysics at Sheffield University. She decided that she wanted to inspire other young people, so moved to Bristol to complete a PGCE in Secondary Science. She particularly loves creating fun and absorbing materials to help students achieve their exam potential.

    Caroline Carroll

    Reviewer: Caroline Carroll

    Expertise: Physics & Chemistry Subject Lead

    Caroline graduated from the University of Nottingham with a degree in Chemistry and Molecular Physics. She spent several years working as an Industrial Chemist in the automotive industry before retraining to teach. Caroline has over 12 years of experience teaching GCSE and A-level chemistry and physics. She is passionate about creating high-quality resources to help students achieve their full potential.