2.4 - Energy and efficiency Flashcards
What is energy measured in?
joules, J in all its forms
What is input energy?
The total energy supplied to a machine
How can you work out the total input energy of a machine? Why does this work?
Using the conservation of energy:
input energy = useful energy transferred + energy wasted
What makes a machine more efficient?
The less energy that is wasted by a machine, the more efficient the machine
What is the equation for efficiency?
Efficiency = useful energy transferred/total energy supplied (x100%)
How can efficiency be displayed?
It can be left as a fraction or multiplied by 100 to make a percentage
What is the unit for efficiency?
Ha ha trick question.
Efficiency is a ratio, which means it doesn’t have a unit
What is the only appliance that can be 100% efficient?
An electric heater, which usefully transfers all electrical energy supplied to it by heating its surroundings
How can we represent the energy transfer through an appliance?
A Sankey diagram
You can make machines more efficient by reducing what four things?
- friction
- air resistance
- electrical resistance
- noise due to vibrations
