1. Energy Transfers Ashfield Direct Learning Madeleine Mantock Ks4 Energy

2. What are energy transfers?  There are three kinds of thermal energy transfer: conduction, convection and radiation.  The transfer is always from hot to cold. Radiation Convection Conduction

3. Transfers in Solid, liquids and Gases?  Metals are very good conductors.  Non metals are usually poor conductors (insulators).  Gases are very poor conductors.

4. What are energy transfers?  Energy is continually being transferred to and from all objects by radiation, even through empty space (a vacuum).

5. How energy is transferred  When devices transfer energy, only part of it is usefully transferred  The remainder is transferred in some non-useful way, and therefore is ‘wasted’ or lost to the surroundings 100 joules/sec Electrical Heat Light 80 joules/sec (wasted) 20 joules/sec (useful)

6. Energy Efficiency  “Efficiency” is the ratio of useful energy to wasted energy  To calculate the efficiency of any device, you need to use the following formula: Efficiency = Useful energy transferred by device Total energy supplied to device

7.  Using the efficiency formula calculate the efficiency of this T.V. set Calculating efficiency Electrical 200 joules/sec Heat Light Sound 150 joules/sec 20 joules/sec 30 joules/sec Efficiency = 50J x 100% = 25% 200J Remember A T.V. has both light and sound as useful energy transferred. Hence the calculation is;