P1-Energy Stores And Systems Flashcards
What happens when energy is transferred to an object
When energy is transferred to an object it is transferred to one of its energy stores
What are the 8 different energy stores
Kinetic Chemical Gravitational Elastic Thermal Magnetic Nuclear
Kill chemistry get every (periodic) table make them not legal
What are the four different energy transfer pathways
Mechanical pathway -(when a force acts and something moves )
Electrical pathway-(When a current flows)
By heating
By radiation
What is a system
A system is one or multiple different objects
What happens when a system changes
When a system changes energy is transferred. Energy can be transferred into or out of the system , between different objects in a system or between the objects energy stores
What happens to the energy in a kettle when the water boils
When the water boils in a kettle energy is transferred to the water from the kettles heating element through the electrical pathway by heating. This transfers energy to the thermal energy store of the water and causes it to increase in temperature
How else apart from heating can energy be transferred
Energy can be transferred when work is done.
Work is done when a current flows or a force moves an object
(Work done means the same as energy transferred
How is energy transferred when an object is projected upwards
When an object is projected upwards the initial force of the object going upwards causes work to be done. This causes energy to be transferred from the chemical energy store of the persons arm to the kinetic energy store of the object and the arm
What happens to energy when a ball is dropped from a height
When a ball is dropped from a height it is accelerated by gravity and the gravitational force does work. This causes energy to be transferred from the gravitational potential store of the ball to the kinetic energy store of the ball .
What happens to energy as a car brakes
When a car breaks the friction between the cars breaks and its wheels causes work to be done as it slows down. Energy is transferred from the kinetic energy stores or the wheels to the thermal energy stores of the surroundings
What happens to energy in a collision between a car and a stationary object
In a collision between a car and a stationary object the normal contact force between the two objects causes work to be done . This transfers energy from the kinetic energy store of the car to the elastic and thermal energy stores of the object and car body. Some energy may also be transferred away by sound waves
How do you calculate the kinetic energy stored in an object
Kinetic energy (j) = 1/2 mass(kg) x speed (m/s)^2
How do you calculate the energy in the gravitational potential store of an object
GPE (j) = mass(kg)x height(m)x gravitational field strength(n/m)
What happens when an object falls
-When an object falls energy is transferred from the objects gravitational potential energy store to its kinetic energy store
-Without air resistance
Energy lost from the gravitational potential energy store = energy gained in the kinetic energy store
-With air resistance some of the energy is transferred to other stores
How do you work out the amount of energy in the elastic potential energy store
Elastic potential energy (j)= 1/2 spring constant x extension ^2
Ee=1/2ke^2
What is the conservation of energy principle
The conservation of energy principle states that energy can be transferred usefully,stored or dissipated but never created or destroyed
What is energy dissipation and when does it happen
- When an energy transfer takes place some energy is always transferred to somewhere you dont want it to go. This is called energy dissipation
- Energy dissipation is often called wasted energy as the energy goes to a store that is not useful e.g the thermal energy stores of surrounding
What happens to the energy stores in a phone
A mobile phone is a system and when you use it energy is tranferred to the chemical energy store of the battery. Energy is also dissipated in this transfer to the thermal energy store of the phone
What happens when energy is transferred in a closed system
When energy is transferred in a closed system energy transfers still occur within the system but there is no overall energy change because no energy leaves the system
What is the equation for power
Power(watts)=energy transferred
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Time
What is a powerful machine
A powerful machine is a machine that tranfers lots of energy over a small amount of time
If two identical cars raced the one with the more powerful machine would win as it would transfer more energy over less time
What is efficiency of an object
The less energy that us wayed in an energy store , the more efficient an object is
An objects efficiency can be improved by lubricating an object,making it more streamlined or insulating an object
How do you calculate efficiency
Efficiency = useful output energy transfer
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Total input energy transfer
Why is no device (except for electric heaters ) 100% energy efficient
No device is 100% energy efficient as energy is always transferred to wasted sources. The wasted energy is tranferred to the thermal energy store
