p7 Flashcards
Object thrown upwards
KE transfers to GPE
then GPE transfers back into KE as it falls down
Object projected up a slope
KE to GPE
Reverse when rolling back down
Moving objecting hitting a wall
KE transferred to EPE when it gets squashed
Object accelerated by a constant force
Force does the work on the object
Transferring energy from whatever applies the force to KE in the object
Vehicle slowing down
KE of vehicle transferred to heat energy from friction between brakes and wheels and the wheels and road
Kettle boiling water
Electrical energy into thermal energy in water
Heating
Parci,es gain more KE
Temp in object increases as energy supplied is used to overcome SHC
Work done
Force itself doesn’t not give the object energy but the force applied over a distance requires energy- work done
When is energy lost
When it’s transferred into other forms, instead of the desired form (not acc lost, just wasteful)
How is energy typically lost in electrical systems
Heating of wires
Transferred from mains(AC supply) or batteries, (DC)
How do motors lose energy
They heat up when moving, due to inefficient contacts between the wire and spinning coil
What are power ratings
Show the power and voltage of an electrical appliance. This can be used to find current and how much energy used for the item. Larger power, more energy used per second
Therefore increased efficiency
How do you increase efficiency in electricity
Decreasing current, as power loss in heating wires is due to current snd resistance
Other ways to reduce efficiency
Recycling waste energy or prevent it from dissipating
Lubricating mechanical systems (reduced friction and heat loss)
Thermal insulation (ensures all heat energy is used, and not lost to surroundings)
How does insulation help reduce loss of heat energy
Without insulation, gaps between outer walls and inner walls contain forms air, meaning convention currents form, losing energy, in this case, rate of cooling is high
With insulation, fibreglass or cavity wall insulation, fills the cavity preventing heat from being lost as convention currents can’t form. Material also weakly conducts heat so the rate of cooling is low
Thicker walls also result in a lower rate of cooling
What is nuclear energy
Atomic nuclei releasing energy in nuclear reactions
Mechanical energy transfer
Object moving due to force acting on it
Electric energy transfer
Charge moving thru a pd
Heating energy transfer
Energy from a hotter object transferred to a colder object
Radiation energy tranfer
Energy transferred by waves
