4 ENERGY Flashcards
Unit for mass
Kilogram (kg)
Unit for energy
Joule (J)
Unit for distance
Metre (m)
Unit for speed
Metre/Second (m/s)
Unit for acceleration
Metre/Second^2 (m/s^2)
Unit for force
Newton (N)
Unit for time
Second (t)
Unit for power
Watt (W)
Name the energy stores
- Chemical
- Kinetic
- Thermal
- Magnetic
- Gravitational
- Elastic
- Electrostatic
- Nucleur
Name the energy transfers
- Mechanically
- Electrically
- by heating
- by radiation (light + sound)
State the principle of the conversation of energy
Energy cannot be created or destroyed, only transferred from one store to another
Effeciency equation
Efficency = Useful energy output / Total energy input
How do you get energy effeciency as a percentage
Multiply by 100
Unit for effeciency
No unit
How to draw a sankey diagram
- Label everything with input/output, store and effeciency
- Width of arrows represent effeciency
Describe the process of conduction
- Heated particles vibrate
- Pass energy to neigbhouring particles via collisions
- Energy passes throughout material, so matter must be in contact for particles to collide (solid)
Why are metals good conductors of heat
Free electrons for more collisions
Why are solids good conductors
Particles are close togetherm and have strong forces between them
Why are insulators bad at heat transfer (conduction)
They have no free electrons, so there are less collisions
Why are liquids and gases bad at transferring heat by conduction
Particles are far apart, so collisons transferring energy are more difficult / less succsesful
Describe how to carry out a conduction experiment
- Attach a metal rod to clap stand with a bunsen burner at the other end
- Attach paperclip at equal distance (ruler) along rod, with vasaline
- Whit stopwatch, record time taken for each paperclip to fall
- Repeat for rods of different materials
Describe how convection works
- Hot object heats the air above it
- Particles in air vibrate more
- Particles in air spread out, and become less dense
- Less dense air rises
- As hot air cools, it falls and the denser coled air replaces the hot air
- Sets up a convection current
What states does convetion occur in
Solids and Liquids
State ways to reduce convection currents
- Foam
- Lid
- Vaccum
THEY ALL TRAP AIR
State how to observe a convection current forming
Place a dye into the corner of a large trough of water and only heat that side and observe the pattern
How does radiation (heat transfer) travel, and why is that special
Travels as EM waves - Can travel through a vaccum
What is the link between surfaces when radiating and absorbing heat
Matt and black materials are good, whereas shiny and white/silver materials are bad
How does the rate of cooling differ when compared with room temperature
- Rate of cooling is greater when object is hotter
- Larger difference betwen water, and room temperature
- On a graph, an original steep gradient would level out (more energy transferred more rapidly)
Describe different experiments to investigate radiation
- Place silver and black tin on mat, and fill with boiling water
- Record initial temperature, and record in stages with thermometer
OR
Use a leslie cube (metal) with 4 different surfaces, using an infrared ray to observe temperatures
How does loft insulation minimise heat loss
- Fibreglass is an insulator with pockets of air
- Air is poor conductor, as trapped air cannot move
- Prevents convection current being set up
State the 3 ways that heat loss can be minimised in a home
- Loft insulation
- Double glazing
- Shiny foil behind radiators