Deck 1 = Physics start of year- 10/10/13 Flashcards
revision for half term tast
What is energy measured in?
-Joules.
Name types of energy?
-Chemical potential, kinetic, gravitational potential, potential, elastic potential, nuclear potential, thermal energy, electrical, radiation.
What is energy measured in?
-Joules.
Law of energy conservation?
-Energy can not be destroyed, During each transformation, the total amount of energy stays the same.
What happens to GPE as you climb?
-It increase.
Gravitational field strength on earth?
-10 newton per kilogram.
What is the efficiency equation?
-Efficiency = useful power output (w) over power input (w).
Work done =
-Energy transformed measured in J.
Unit for energy efficiency?
-No unit, or percentage.
What is kinetic energy measured in?
-J
What is thermal energy measured in?
-J
What is chemical potential measured in?
-J
What is power measured in?
-W
Define work?
-Work is done whenever a force make something move. The greater the force and the greater the distance moved, the more work is done.
One joule=
-One newton meter.
If an engine does 2000J of useful work in 2 seconds, what is its power output?
-1000J
Engine does 25J of useful work for every 100J of energy supplied, what is its efficiency?
-0.25 or 25%
Rearrange GPE=mgh to find H?
-GPE over mg = H
Equation for Kinetic energy?
-KE=0.5mv2 (squared).
The higher the temp…
-The faster the atoms moving.
Absolute zero =
-273oC 0K this can never be reached because you need something colder to take away the thermal energy.
When we say to things are at the same temp, this means…
-They do not have a thermal energy transfer.
Standard atmospheric pressure.
-101325 Pa.
When you put a hot and a cold thing together…
-The hot thing loses its kinetic energy and the cold thing gains Kinetic energy.
Define Conduction?
-This is when thermal energy or randomized kinetic energy is transferred from one place to another due to collisions between particles. This happens more quickly in metals.
Particles in hot objects…
-Vibrate with a large amplitude. large then that of liquids and gasses.
What is convection?
-Liquids and gases are poor thermal conductors however they are free to circulate and they are also aloud to carry thermal energy from one place to another quickly.
Define convection current?
-Liquids or gasses become less dense when they are heated making them rise. they then cool and sink. It happens in a circle, this i called a convection current.
How can you reduce convection?
-By holding or trapping air in place.
How does this happen with a fridge?
-Cold air sinks because it is more dense and the hot air rises. then the hot are is sucked out the fridge.
How does conduction work?
-Particles vibrating with big amplitude transfer their kinetic energy to there neighbor through collisions.
How does convection work?
-Heated fluids expand, becoming less dense and rising. cooler fluids do the reverse, this sets up a convection current.
How does Radiation work?
-All objects emit inferred or thermal radiation. Hot objects emit more. When this energy is absorbed energy in transformed.
How do we minimize conduction?
-Use insulator.
How do we minimize radiation?
-Paint an object white or give it a silver reflective surface.
How do we maximize conduction?
-Use a good conductor such as copper.
How to maximize convection?
-Allow the fluid to move freely.
How to maximize radiation?
-Paint an object black, this maximizes emissions and absorption.
What is time measured in?
-Seconds (s)
What is energy transferred measured in?
-J
What is work done measured in?
-J
Efficency equation?
-Useful power over total power input.
Equation for power?
-Energy transferred (j) over time (s).
Power Work done equation, Power =
-Work done over time. Wd/t.
Power Energy equation, Power=
-Energy (j) over time (s).
How to make a house more energy efficient?
- Loft insulation.
- Double glazing.
- For doors and windows use draft exclude.
What is the process called when a material can only conduct in a liquid form?
-Electrolysis.
