# Physics 1a

bethf6's version from 2015-05-14 17:30

## Section

What heat transfers uses particles?Conduction and convection
What are the 3 heat transfers?Conduction, convection and radiation
What is the main heat transfer in solids?Conduction
An object that is hotter than its surroundings emits...?more radiation than it absorbs
An object that is colder than its surroundings emits...?less radiation and absorbs more radiation.
What do dark, matt surfaces do to infrared radiation?It absorbs it well
What do light, shiny surfaces do to infrared radiation?It reflects it well
What are the three states of matter?Solids, liquid and gases
What happens when you heat a substance?It gives more kinetic energy eg. they vibrate and move faster
What is conduction?The process where vibrating particles pass on their extra kinetic energy to neighbouring particles
What solids is conduction usually faster in and why?Denser objects because the particles are closer together so will collide more often and pass energy
Why do insulators insulate heat?There are larger spaces in their particles so they conduct heat much more slowly
When does convection occur?Convection occurs when the more energectic paticles move from the hotter region to the cooler region and take their heat with them
What happenes when a particle is heated?It expands and becomes less dense so rises (if it is a liquid or gas)
What happens in conduction?A paticle is heated and rises because it expands and becomes less dense, then when it rises it is away from the heat so cools down and falls back because it becomes more dense.
What are convection currents based on?Changes in density
At what part of an object is heat energy radiated from?The surface
What can help the amount of waves emitted?The surface area
What does a flask have to help insulating heat? *Vacuum so no paricles for convection and conduction to take place *Walls that are shiny to reflect heat into it *Insulating foam to minamise heat conduction *The stopped that is made out of an insulator to reduce conduction.
Why do the hairs on our arms stand up?To trap a thicker layer of insulating air around the body
What happenes when you are too warm?The blood goes closer to the surface so it can emit more radiation and more heat can be lost
Why do desert foxes have large ears?There is more surface area so can easily loose heat
What is the most effective method of insulationThe one that gives the biggest annual saving
What is cavity wall insulation?Foam squirted into the gap between the bricks reduces convection and radiation.
What is loft insulation?A thick layer of fibregalss wool laid out across the whole loft floor
What is draught proofing?Strips of foam and plastic around doors and windows stop draught of cold air blowing in
What is a hot water tank jacketLagging suck as fibreglass wool
What is the u-value?The u-value shows you haow fast heat can transfer through a material eg. the best insulator has a lower u-value
What is the units for the specific heat capacity?Joules
What does the specific heat capacity tell us?How much energy things can store
What does m stand for in the specific heat capacity equation?Mass (g)
What does c stand for in the specific heat capacity equation?Specific heat capacity (j/kg degrees)
What does o(feta stand for in the specific heat capacity equation?Temperature change (degrees)
What are the nine types of energy?Electrical energy, light energy, sound, kinetic, nuclear, thermal, gravitational potential, elastic potential and chemical
What types of energy are forms of stored energy?Potential and chemical
What can energy never be?Created or destroyed
What can energy be transferred by?Energy can be transferred usefully from one form to another, stored or lost
When is energy useful?When it can be converted from one form to another
What energy transfers do electrical devises such as televisions use?Electrical energy to light, sound and heat energy
What does it mean when something is not very effiecient?There is alot of wasted energy
What does it mean when something is efficient?There is not much wasted energy
What is the efficiency measured in?Percentages