GCSE P1 Energy Equations and P2 Energy transfer by heating Flashcards
What is the principle of conservation of energy?
Energy cannot be created or destroyed. This means all systems do not lose energy.
Energy transferred is the same as…
Work done
Work done equation
Work done (J) = Force applied (N) x distance moved along the line of action of the force (m) W = F x s
Change in object’s Gravitational potential energy store equation
Weight (N) x change of height (m)
J = N m
Change of gravitational potential energy store (J)
GPE E = mass (kg) x gravitational field strength (N/kg) x change of height (m)
/\ E = m x g x /\h
Kinetic energy (J) equation
1/2 x mass(kg) x (speed)^2
1/2 x m x v^2
Elastic potential energy (J) equation
1/2 x spring constant(N/m) x (extension)^2
1/2 x k x e^2
Energy efficiency equation (%)
Useful output energy transferred by the device / total input energy supplied to the device
X 100
Power equation (W)
Energy transferred to appliance, E (Joules,J)/time taken for energy to be transferred, t (seconds,s)
Efficiency of Power %
Useful power out / total power in (x 100)
Energy transferred (Joules, J) equation
Mass, m (kilograms,kg) x specific heat capacity, c (J/kg°C) x temperature change (°C)
1.1 How do you show how energy is transfered?
You show this by showing a flow diagram
1.1 How can energy be transfered?
It is transfered by heating, waves, electric current or by a force when it moves an object.
1.1 What are all the fundamental energy stores?
Chemical energy stores, Kinetic energy stores, Gravitational potential energy stores, Elastic potential energy stores, thermal energy stores.
1.1 Show the chemical energy transfers in a battery
Chemical energy —-> Electrical energy —-> Light energy + Thermal energy
1.1 Show the energy transfer of an object falling
Gravitational potential energy –> kinetic energy –> thermal energy + sound energy
1.1 Chemical energy store Def
It includes fuels, foods, or the chemicals found in batteries
1.1 Kinetic energy Def
Describes the energy of an object moving
1.1 Gravitational Potential Energy DEF
Used to describe the energy stored in an object because of its position such as an object above the ground.
1.1 Elastic Potential Energy Store DEF
Describes the energy stored in a springy object when you stretch or squash it
1.1 Thermal Energy store DEF
The energy a substance due to temperature
1.2 Is energy an open or closed system?
It is a closed system because there would be no net change to the energy stored in system.
1.2 Describe the energy transfer of a bungee jumper
When the rope slacks, tightens and after it reaches the bottom
When the rope is slack: GPE energy store —> kinetic energy store
When the rope tightens: Kinetic energy store –> Elastic potential energy store (this gets bigger when the rope gets stretched)
After reaching the bottom: Elastic potential energy –> kinetic energy —> gravitational potential energy.
Doesn’t go back to original height
1.2 What does a pendulum show?
As it swings up and down, its gravitational potential energy store decreases as the kinetic energy store increases. At the highest point, it is the maximum GPE, at the lowest point, it is at the maximum kinetic energy.
1.3 What is work done?
It is essentially energy
1.3 How does work done happen on an object
Work is done on an object when a force makes the object move. Think of when World’s Strongest Man carrying pulling the lorry.
1.3 How does work done overcome friction?
Work done to overcome friction is transferred as energy to the thermal energy stores of the objects that rub together and to the surroundings.
1.4 What happens when an object moves upwards? And downwards?
The GPE store increases as the object goes upwards, as it goes downward, it decreases (this is equal to the work doen by the gravitational force acting on it).
1.4 What does work done depend on?
- How far it is moved (change in height)
2. IT’S WEIGHT
1.5 What is the energy in kinetic energy store depends on?
It depends on the mass and its speed.
1.5 How do you investigate kinetic energy stores with a ball and light gates?
With a ball measure the mass and let it roll down, measure the velocity from the light gates
1.5 What is Hooke’s law
Force x extension (on a graph if it is elastic, they are directly proportionate but if it is plastic, it does not regurn to its original shape
1.6 What is Useful energy?
Energy in the place we want it and in the form we need it.
1.6 What is wasted energy?
It is the energy that is not useful energy and is transfered by an undesired pathway. It dissipates to the surroundings.
1.7 How do machines stop friction and waste from thermal energy?
Lubricate the moving parts to reduce friction.
1.7 How to stop making wires hot?
Use less of them
1.7 How to stop air resistance in objects which will oppose its motion?
Streamline the shale of moving objects reducing air resistance
1.7 How to reduce sound energy in appliances
Tighten loose parts to reduce vibration
1.9 What is Power?
It is the rate of transfer energy
1.9 How to see how much power is wasted?
Total power in - useful power out
2.1 Testing rods of different materials as conductors
Equipment: Bunsen Burner, wax, tripod, waxed rods
What will it show: The one where the wax will fall is the best conductivity, the one where the wax will fall the last is the best insulator.
2.1 Which material is the best conductor
Metal
2.1 Which non-metals have the worst conductors/best insulator
Wool or fibreglass
2.1 The higher the thermal conductivity the …. rate of energy transfer
The higher the rate of energy transfer through it.
2.1 What does a layer of insulating material depends on?
- The temperature difference across the material.
- The thickness of the material.
- The thermal conductivity of material.
2.2 Do all objects emit and absorb infrared radiation?
Yes!
2.2 The higher the temperature of an object, the … infrared radiation
The more infrared radiation it emits in a given time
2.2 What is a perfect black body?
They absorb all infrared radiation that hits it. Doesn’t reflect or transmits it.
2.2 If an object is a good absorber, is it a good emitter?
Yes, an example is a perfect black body which is the best possible emitter.
2.2 An object that has a constant temperature, emits radiation (something about wavelengths)
Emits radiation across a continuous range of wavelengths.
2.3 What is the best emitter of radiation
Matt black surface which is the !best absorber but worst reflector!
2.3 What is the worst emitter of radiation?
Silver which is the !worst absorber but the best reflector! Think of the experiment with the beaker
2.4 What is specific heat capacity
The amount of energy needed to change the temperature of 1kg of the substance by 1K (kelvin is more scientifically accurate)
2.4 If an object is bigger is it quicker/slower to raise its temperature
It is slower to increase its temperature when it is heated.
P2.5 Loft insulation
It reduces the rate of energy transfer through the roof. The air between the fibreglass also decreases the rate of conduction. More layers also increases insulation.
2.5 Cavity wall insulation
Reduces the rate of energy transfer. The cavity of an outer wall is the source between the layers. Insulation is also pumped into the cavity.
It traps the air in small pockets, reducing the rate of energy transfer by conduction.
2.5 What does Aluminium foil do to radiation
It reflects radiation away
2.5 What are double glazed windows and how do they work?
Two glass planes with dry air between them. Dry air is a good insulator which reduces the rate of energy transfer. Vacuum also prevents the energy transfer by convection
