Physics Units 1-4 Flashcards
How do you calculate the amount of elastic potential energy stored in a spring?
E = ½ ke2
What happens to the gravitational potential energy of an object as it falls?
It changes to kinetic energy
What is specific heat capacity?
The energy required to raise the temperature of one kilogram of the substance by 10C
What is power?
Work done per unit time OR energy transferred per unit time
What is a power of one watt equal to?
1 J/s
What is the principle of conservation of energy?
Energy cannot be created or destroyed just transformed from one form into another
How could you reduce unwanted energy transfers in machinery with moving parts?
Oil/lubricate
How could you reduce unwanted energy transfer from a cup of coffee?
Insulate
Name 2 renewable energy resources available for use on earth.
Wind/wave/tidal/solar etc
Name 2 non-renewable energy resources available for use on earth.
Coal/oil/gas/nuclear
What is meant by a renewable energy resource?
Will not run out
What is electrical current?
Flow of charge/flow of electrons
What do you know about the current at any point in a series circuit?
It is the same
What happens to the resistance of an LDR as light intensity increases?
Decreases
What happens to the resistance of a thermistor as one temperature increases?
Decreases
Is mains electricity ac or dc?
a.c.
What is its frequency?
50Hz
What is its p.d?
230V
What is the difference between ac and dc?
a.c. - changes direction d.c. - one direction
What colour are the insulation coverings on live, neutral and earth wires?
live - brown, neutral - blue, earth - green & yellow
What is the earth wire there for?
As a safety device
What is the p.d. between the live wire and the earth?
230V
When does the earth wire carry a current?
If there is a fault
What are the 2 different equations to calculate power in an electrical circuit?
Power = IV
Power = I2R
What is the National Grid?
A system of cables and transformers linking power stations to consumers
What does a step up transformer do?
Increases voltage
How does an insulator become charged when rubbed with another insulating material?
Friction causes electrons to be removed from one and given to the other
What is density?
Mass per unit volume
Why is a solid more dense that a gas?
Particles are closer together
What is internal energy?
Total potential and kinetic energy of all the particles
What is specific latent heat?
The energy required to change the state of one kilogram of a substance without a change in temperature
What happens to the motion of molecules in a gas if you increase the temperature?
Move faster
What happens when you do work on a gas?
Increase internal energy / increase temperature
What is the radius of an atom?
1x10-10 m
How many times smaller is the radius of a nucleus than an atom?
10,000 times
Electrons are found in different what?
Energy levels
Why are atoms neutral?
Same number of protons and electrons
What is the atomic number of an element?
Number of protons
What is the mass number of an element?
Number of protons and neutrons
What is an isotope?
Atoms of the same element with the same number of protons and different number of neutrons
How do you form a positive ion?
Lose electrons
Why do some atoms decay?
They are unstable
What is meant by the activity of an atom?
The rate at which a source or unstable nuclei decay
Which type of radiation is the most ionising?
Alpha
Which type of radiation is the least penetrating?
Alpha
What is an alpha particle?
2 protons and 2 neutrons / He nucleus
What is a beta particle?
Fast moving electron
What is gamma radiation?
Electromagnetic radiation
What is the half-life of a radioactive isotope?
The time it takes for half of the nuclei in a sample to decay
What is radioactive contamination?
The unwanted presence of materials containing radioactive atoms on other materials
What is irradiation?
The process of exposing an object to nuclear radiation
Name a source of background radiation?
Cosmic rays / rocks / fallout from nuclear weapons / nuclear accidents
Name a use of nuclear radiation in medicine?
Exploration of internal organs / control or destruction of unwanted tissue
What is nuclear fission?
Splitting of large nuclei
What usually needs to happen for fission to occur?
Neutron to be absorbed
What is nuclear fusion?
Joining of small nuclei