Energy-educake Flashcards
What is the measurement for the amount of energy an object can store
Joules(J)
When is kinetic energy used
When an object is moving
When is gravitational potential energy used
It is used when an object had been lifted up
When is elastic potential energy used
When an object has been stretched or squashed
When is chemical energy used
When an energy is stored in chemical bonds
When is thermal energy used
When an object has been heated
Energy from one energy store can be ___________ to other energy stores
Transferred
When is energy transferred
When an object or group of objects changes or moves it is being transferred
A battery powered drill transfers energy from its chemical energy store to its kinetic energy store as well as to thermal energy stores of the drill and the surrounding
When energy is transferred what does not change
The total amount of energy
If a drills battery transfers 500 J of energy from chemical energy store and 400J of energy ends up in the kinetic energy store so how much is transferred to the thermal energy store
100 J is transferred to the thermal energy store
When energy is transferred what happens to some of the energy
Some of the energy transferred is useful and some of the energy is wasted
When is energy useful
When it is transferred to the energy stores we want to be in
When is energy wasted
When it is transferred to the energy stores that we don’t want it to be in
When we use a battery powered drill what energy store increase is useful and why
An increase in its kinetic energy store is useful because we want the drill bit to rotate
What is an increase in thermal energy when using a battery powered drill
It is wasted energy because we don’t want the temperature to increase
What happens to wasted energy
It is not destroyed and does not disappear but we cannot easily use it
What does efficiency tell us
It tell us what proportion of energy is transferred usefully
What can efficiency be given as
A percentage or decimal
What equation is used to calculate the efficiency of a device or energy transfer
Efficiency = useful energy output / total energy input
What is the efficiency if the drills battery provides 500 j of chemical energy but only 400 J is transferred to kinetic energy
Efficiency = 400 / 500 = 0.8
How do you get the answer to your efficiency as a percentage
We can multiply it by 100
0.8 x 100 =80 %
What can the useful output energy never be greater than
The total input energy
