8H Energy Flashcards
What is a Shadouf?
A type of lever used by ancient Egyptians
What is a machine?
Something that helps us to do work.
What can a force do to energy?
A force can transfer energy.
When is work done?
When a force is used to transfer energy.
What is the unit for energy?
Joules (J)
What 2 things affect work done?
Force applied and distance moved
What is displacement?
The shortest distance from a start to and end point.
What is the equation to calculate work done?
work done (J) = force (N) x distance (m)
How do machines make work easier?
They reduce the force needed to make something work.
Why isn’t a tractor a human powered machine?
They are powered using sources of energy other than us
Why do humans require the use of machines?
There is a limit to how much force we can supply.
Give an example of a common machine.
Door handle, toilet flush, tap, pedal bin
How does a lever reduce work?
It reduces force by increasing distance.
How does a screwdriver help to open a tin of paint?
The screwdriver increases the distance the force is acting over.
How do wheels reduce work done?
They reduce friction.
What machines are present in a bicycle?
Levers, gears and wheels.
What state of matter does conduction occur through?
Solids
How do particles in a solid move?
They vibrate in place
What is a thermal insulator?
Materials which are not good at allowing the transfer of energy through them.
Give an example of a thermal conductor.
Metals
Which states of matter does convection occur in?
Liquids and Gases (Fluids)
What is a convection current?
A current in a fluid that allows the transfer of heat energy.
What does radiation travel as?
A wave
Describe the frequency of infrared radiation.
The frequency is lower than red light.
Name three places where it is common to have insulation in our homes.
Cookers, fridges, walls, loft, etc.
What is something called if energy passes through it at a slow rate.
Insulator
In the experiment shown- what is the independent variable?
Material the rod is made from.
In the experiment shown- what is the dependent variable?
Time taken for the pin to drop.
In the experiment shown- name 1 control variable.
Length of the rod, placement of pin, time heat is applied.
When insulating something, why should fluids not be allowed to flow?
Fluids can transfer energy through convection.
What type of materials are good at reflecting waves?
Shiny objects.
Why do builders put plastic foam between walls for insulation?
The foam contains air pockets- good insulator.
Give an example of a use of a thermal conductor.
Saucepans, radiators,
Give an example of a use of a thermal insulator.
Food containers, loft insulation.
What is the independent variable in this experiment?
The insulation material.
What is the dependent variable in this experiment?
Temperature change over time.
Why is the experiment carried out on a heat-proof mat?
To minimise heat loss through the base of the can.
What is the function of the lid?
To minimise heat loss through convection.
Identify a control variable for the experiment.
Number of layers of insulation material, starting temperature, time the temperature was measured.
How will you know which material is the best insulator?
The test where the temperature decreased the least.
How will the type of material/ number of layers be represented on the graph?
Curves on the same axis
Why do we need to draw a graph of our data?
To see any patterns in the data
How can you easily measure thermal energy transfer?
Monitor temperature
In what direction is thermal energy transferred?
From a warm object to a cooler object
What is thermal equilibrium?
An equal temperature in all objects.
What is a vacuum flask made from?
2 glass layers covered in a reflective surface.
What is a vacuum?
An area with no particles.
Why is a vacuum useful?
Thermal energy can not be transferred by conduction of convection through a vacuum.
Why is the glass silvered?
To reflect the radiation.
What is the function of the lid?
To stop heat loss through convection.
