TOPIC 1 Energy Flashcards
Define energy
If an object has energy, it has the ability to make other objects move.
Name the 8 energy stores
Thermal energy stores
Kinetic
Gravitational Potential
Elastic potential
Chemical
Magnetic
Electrostatic
Nuclear
What does the total energy of a system equal
Total amount of energy in = total amount of energy out
What happens to energy during an energy transfer
This energy goes into the atmosphere
The energy of the surrounding increase.
It will cause an increase in the thermal energy of its surroundings
therefore particles move faster
What is a system
A system is an object or group of objects
Example of a closed system
When do these examples become open systems
Toy car travelling down a lamp
A lit candle/A WAX CANDLE THAT HAS NOT BEEN LIT
Car
Stops becoming closed system
Car stops becoming a closed system when fuel is put in (increases chemical energy store)
By increasing the length of the candle (adding more wax) -increases chemical energy store of the candle)
The total amount of energy is not fixed
What is a closed system
A close system is an object (or a group of objects) where the total amount of energy is fixed.
What is the law of the conservation of Energy
The law of the conservation of energy states that in any system energy can be transferred usefully, stored or dissipated, but cannot be created or destroyed.
what does DISSIPATED mean
dissipated means wasted
When does a closed system stop becoming a closed system?
A system stops becoming a closed system when energy is transferred into the system or when energy is transferred away from the system.
How does using a low energy light bulb increase efficiency
A low energy light bulb increases it’s efficiency by reducing the thermal energy being produced (saves energy)
it reduces the heat energy produced
How is an electric motor designed to be efficient
Electric motors are designed to be efficieint as they have been designed to produce less heat
what can be done to objects to reduce the energy wasted and to increase efficiency,
to reduce the energy wasted and to increase efficiency objects can be designed to create less waste energy.
How can the efficiency of an electric motor be increased
The efficiency of an electric motor can be increased by reducing friction by lubricating moving parts
Friction can be reduced by lubricating moving parts
How can the efficiency of a house in winter be increased
Insulate the house to reduce the amount of heat energy lost to the outside
Explain why the bungee jumper does not return to their original height after the jump
The bungee jumper doesn’t return to their original height. This is because some of the energy was transferred to the thermal energy store of the surroundings as the rope stretched and then shortened again
How to describe the energy transfer that occurs when a person is falling and reaches the ground
As the person falls, their G.P.E store turns into their kinetic energy store
When the person reaches the ground, their kinetic energy store is transferred to the thermal energy store of the surroundings. Some of the dissipated energy is transferred away by sound waves to the surroundings
The air resistance acting against the falling person will cause an increase in the thermal energy store of the air (surroundings)
What is the net change in total energy of a closed system
A system where neither matter nor energy can enter nor leave.
The net change in total energy in a closed system is always zero.
what happens when you increase the energy of a particle
If you increase the energy of a particle, the particle will move faster
Where is waste energy usually transferred to
The waste energy is transferred to useless thermal energy stores
Describe the energy transfer that takes place when two cars collide with each other
As the cars collide, their kinetic energy stores turns into thermal energy store of the surroundings. Some of the energy has also been transferred away (lost) by sound waves to the surroundings
This energy enters the atmosphere causing an increase in it’s thermal energy store.
Explain the energy transfer that takes place in a pendulum
At the top, the mass has the maximum store of gravitational potential energy.
As the pendulum swings down towards the centre, the gravitational potential energy store turns into kinetic energy store.
The mass has the maximum kinetic energy store at the bottom of the swing (since that is where it is moving at the fastest speed)
As the pendulum moves upwards away from the centre, the kinetic energy store turns into the gravitational potential energy store
As the pendulum swings:
Their is friction in the fixed point causing an increase in the thermal energy store of the air
The air resistance acting against the pendulum will cause an increase in the thermal energy store of the air.
What happens when a system changes
When a system changes, energy is transferred. Energy can be transferred into or away from the system, between different objects in the system or between different types of energy stores.
Explain why no device is 100% efficient
No device is 100% efficient as all devices produce some form of waste energy. (most often in the form of thermal energy) , so less than 100% of the input energy is transferred usefully.
Exception: Devices which function it is to produce heat are usually 100% efficient
E.g. if electric heaters produce lots of waste energy, then it isn’t really waste, and would instead count as useful output
Explain how friction (when a car is moving) causes energy to be dissipated
The friction between the car’s wheels and the ground causes the kinetic energy store of the car’s wheels to be transferred to the thermal energy store of the surroundings.
Describe the energy transfer that happens as the bungee jumper continues to fall towards the ground AND come back up to the platform
As the bungee jumper falls, the gravitation potential energy store turns into the kinetic energy store.
As the bungee cord stretches, the kinetic energy store turns into the elastic potential energy store
Elastic potential energy store turns into thermal energy store.
As the rope recoils and the bungee jumper rises, the thermal energy store turns into elastic potential energy store.
The elastic potential potential energy store turns into kinetic energy store.
The kinetic energy store turns into gravitational potential energy store.
The air resistance will cause an increase in the thermal energy store of the air.
Describe the energy transfer that happens when a train uses it’s breaks to stop
The friction on train wheels due to the brakes reduces KE of train to zero. The kinetic energy store of the train is transferred to the thermal energy store of the surroundings. Some of the dissipated energy is transferred away by sound waves to the surroundings
State the methods of energy transfer
Energy can be transferred:
Mechanically (by a force doing work)
Electrically (work done by when a current flows)
By heating
By radiation
How to reduce unwanted energy transfers in the pendulum
We can reduce unwanted energy transfers by reducing friction and air resistance
Use a lubricant on the fixed point to reduce friction
Remove the air particles from around the pendulum to reduce air resistance
What would eventually happen to the pendulum
As the pendulum swings:
Their is friction in the fixed point causing an increase in the thermal energy store of the air
The air resistance acting against the pendulum will cause an increase in the thermal energy store of the air.
(causing The fixed point and air around to get warmer)
Will cause the ke store turn in to thermal energy store
as thermal energy store increases, ke store decreases causing…
This will cause the pendulum to gradually swing with less energy and eventually stop
