Energy - General
What is the basic scientific unit of energy?
Joules
What is kinetic energy?
The energy of something moving.
List 1 energy transfer which happens when you ride a bicycle.
Kinetic energy from:
Feet to Pedals; Pedals to Chain; Chain to Wheels; Wheels to Bike/Rider
List 1 energy transformation a bluetooth speaker does
Electrical to Kinetic; Electrical to Sound; Electrical to Light; Electrical to Heat.
What is the most common type of waste energy?
Heat
What is the Law of Conservation of Energy?
Energy cannot be created or destroyed; it can only be transferred or transformed.
List 2 types of potential energy
Gravitational; Elastic; Chemical; Nuclear
Can heat energy be transferred through a gas by conduction?
Not really.
(Technically yes, but it is so weak and slow that you would never notice it happening.)
List 2 energy transformations a coal power plant does
Chemical Potential to Light; Chemical Potential to Sound; Chemical Potential to Heat; Heat to Kinetic; Kinetic to Electrical; Kinetic to Heat; Kinetic to Sound
If a lightbulb is supplied with 800J of electrical energy, and turns 40J into light energy, how many Joules of heat energy did the lightbulb generate?
(This lightbulb is silent)
800J - 40J = 760J
What is energy?
The ability to do something.
List 2 types of kinetic energy
Sound; Heat; Movement; Electricity
Define "Energy Transfer"
An energy transfer is where some energy of ONE type is moved from one place (or object) to another, without changing type.
Define "Energy Transformation"
A transformation is where some energy changes from one type to another.
What is the formula for percentage efficiency?
(Useful Output / Total Input) x 100%
List 2 units which are commonly used when measuring electrical energy
Amps/Amperes, Volts, Watts, Ohms
What type of energy is stored in the nucleus of atoms?
Nuclear Potential Energy
Describe the stages of a convection cycle
A fluid is heated; its particles spread apart; it floats due to its lower density; it cools down and pulls back together again; it sinks towards the heat source.
When energy is transformed from one type to another, does it also move (transfer) from one place/object to another at the same time?
Not at the same time, no, but sometimes it very quickly (or even immediately) moves/transfers away.
List 2 ways in which an oven might "waste/lose" energy while it is operating
By making noise when it spins the fan.
By leaking its heat into the surrounding area.
What is heat energy, and does Infra Red Radiation count as heat energy?
Heat energy is the kinetic energy of particles such as atoms and molecules. Since Infra Red Radiation is not made of particles, it is technically NOT heat energy.
(We call it heat energy anyway because it causes particles to accelerate.)
How can we measure the amount of chemical potential energy stored in something (like food or fuel)?
What do you have to control to make it a fair test?
Measure how much heat is released when we burn it, by using it to heat some water (with a thermometer in it).
Make sure the heat actually goes into the water.
List 2 transfers of kinetic energy which happen inside a combustion engine
Kinetic energy from:
Burning fuel to Pistons; Pistons to Crankshaft; Crankshaft to Gears; Gears to Axles; Axles to Wheels
List all the energy transformations which happen when you are bouncing on a trampoline (not including waste)
Gravitational Potential to Kinetic; Kinetic to Elastic Potential; Elastic Potential to Kinetic; Kinetic to Gravitational Potential
If a charger is supplied with 120J of electrical energy, and it transfers 109J into the phone battery, where it gets stored as chemical potential energy...
... what percentage (to 2 decimal places) of the energy was lost as heat?
You may use a calculator.
Total Heat: 120J - 109J = 11J
Percentage Heat: (11J / 120J) x 100% = 9.17% (2dp)