10.4- ENERGY AND EFFICIENCY Flashcards
Equation for work done?
work done = force * distance
Equation for output power?
Pout = work done by machine / time taken = Fvt/t = Fv
F- output force
v- speed of object
What does friction in motor bearings + electrical resistance of motor wires mean?
some of the electrical energy supplied to motor wasted
What is usefule energy?
energy transferred for a purpose
Equation for efficiency?
useful energy transferred by machine / energy supplied to machine
work done by machine / energy supplied to machine
What would happen if a petrol engine was insulated to stop heat loss?
engine would overheat
Why is less energy wasted in an electrical motor than petrol engine?
as it doesn’t burn fuel so electric car would be more efficient than petrol car
Why is power station where our electricity is generated typically less than 40% efficient?
partly because we need to burn fuel to produce steam or hot gases used to drive turbines which turn electricity generators
What would happen if turbines were not kept cool in power stations?
they would stop working as the pressure inside would build up + prevent steam or hot gas from entering
stopping heat transfer to cooling system would stop generators working
