Types of Energy
Energy Transformations
Energy Efficiency
Energy in Photos
Mixed Bag
Final Question
100
What type of energy does a moving skateboard have?
Kinetic energy
100
What type of energy transformation occurs when you turn on a light bulb?
Electrical → light energy (and some thermal)
100
When we say energy has been "wasted", what do we actually mean? It has not disappeared — so where did it go?
It was transformed into a form that is not useful for the job — usually heat, sometimes sound
100
What energy transformation is happening here?
Electrical energy → thermal energy
100
What is the unit of energy, and what is its symbol?
The joule, symbol J
200
What type of energy is stored in a battery?
Chemical energy
200
You drop a ball from your hand. What transformation happens as it falls?
Gravitational potential energy → kinetic energy
200
What is the formula for efficiency?
Efficiency = (useful energy out ÷ total energy in) × 100%
200
Trace the energy from the drumstick coming down to the sound reaching your ears.
Kinetic energy → sound energy (and a little thermal)
200
What does the law of conservation of energy state?
Energy cannot be created or destroyed, only transformed from one form to another
300
A stretched rubber band, pulled back and ready to fire, is storing which type of energy?
Elastic potential energy
300
What energy transformations occur when you use a toaster to make toast?
Electrical → thermal energy
300
A globe takes in 100 J of electrical energy and gives out 20 J of light. What is its efficiency?
20%
300
The mat is stretched right out. What energy transformation happens from this moment until they reach the top of their jump?
Elastic potential → kinetic → gravitational potential energy
300
Name two forms that wasted energy usually turns into when a machine is running.
Heat and sound
400
What energy transformation happens when you turn on a hairdryer?
Electrical → kinetic (the fan) + thermal (the heating element), plus sound
400
You rub your hands together quickly. What transformation is happening?
Kinetic energy → thermal energy (and a little sound)
400
Same globe: how much energy is wasted, and what form is most of it in?
80 J, mostly as heat
400
What transformation happens as the car goes over the top and races down?
Gravitational potential energy → kinetic energy
400
In our car practical, where did the car get its energy at the top of the ramp, and what did that energy turn into?
Gravitational potential energy → kinetic energy as it rolled down (plus heat and sound from friction)
500
A skateboarder rolls down a ramp and stops at the bottom without braking. Name the type of energy they had at the top, the type they had at the bottom, and one type the energy ended up as.
Gravitational potential energy at the top → kinetic energy at the bottom → wasted as thermal energy and sound from friction
500
You charge your phone overnight, then use it to play music the next day. Write the chain of energy transformations from the wall socket to the sound coming out.
Electrical → chemical energy in the battery → electrical again → sound (plus heat wasted at each step)
500
A motor takes in 500 J of electrical energy and is 60% efficient. How much useful energy does it produce?
300 J
500
The phone is charging and feels warm when it finishes. Write the transformation, and name the energy that was wasted.
Electrical → chemical energy in the battery; the thermal energy is wasted energy
500
A ball is dropped and bounces, but each bounce is lower than the last. Energy can't be destroyed — so where is it going?
Transformed into heat and sound each time it hits the ground, so less is left as kinetic energy for the next bounce
500
A motor takes in 800 J and is 25% efficient. How much useful energy comes out, and how much is wasted?
200 J useful, 600 J wasted