Power and electrical power

19 April 2023

Keywords: Power, Energy, Weight, Force

ObjectivesUnderstand what power is and be able to calculate it.

HSW: AF5 – Working critically with evidence AF4 – Using investigative approaches

Used before in: lesson 1 – work Will use again in:

PLTS: Team workers – Work collaboratively with others.

Used before in: Science A Will use again in:

Outcomes

• All students should be able to describe what makes an object powerful or not.

• Most students should be able to define power and use the equation.

• Some students should be able to evaluate practical work and describe how to make it more valid and reliable.

Powerful cranes

Which is the most powerful crane? Explain why.

How is power calculated?The power exerted by an object can be calculated using one of two equations:

Time is measured in seconds (s).

Power is measured in watts (W).

Work done is measured in joules (J).

work done

time takenpower =

Remember that work done = energy transferred.

A lawnmower engine does 10

kJ of work in 10 seconds. What is the power of the engine?

Calculating power question 1

= 1,000 W = 1 kW

power =work done

time

= 10,000 / 10

A car transfers 12 mJ of energy in 2 minutes. What is the power of the car?

Calculating power question 2

= 100,000 W = 100 kW

= 12,000,000 / 120

power =work done

time =energy transfer

time

Power, work and time calculations

Anagrams

And finally – we find out – who are more powerful – boys or girls?

• Force x distance = energy• Energy/time = power

Boys: Girls:

Force Dist for 1 rep

reps Total dist

work time power Force Dist for 1 rep

reps Total dist

work time power

Skipping

Lifting

Push ups

Analysis: What conclusion can you draw? Evaluation: was the evidence reliable? Explain.

Energy Gravitational Watts

Heat Power Kinetic

Electrical1 Joule per

secondJoules

Plenary - Multiple-choice quiz