Everything Flashcards
How do you find pressure
Force divided by area
How do you find density
Mass divided by volume
What is 1m3 in cm3
1,000,000 cm3
What is Brownian motion and how does it support particle theory
Robert brown notices that pollen grain in what moved with zigzag random motion: this type of movement of any particles in a suspension is known as Brownian motion
It supports the particle theory of different states of matter. Large heavy particles (eg smoke) can be moved with Brownian motion by smaller lighter particles (eg air) at high speeds
What is absolute zero in degrees c
-273
What direction to magnetic field lines always point
North to South
How do you create a uniform field between two magnets
Placing the north and south poles or two permanent bar magnets near each other creates a uniform field between the two magnets
What is the motor effect
When a current carrying wire is put between magnetic poles the two magnetic fields affect one another. The result is a force in the wire causing to move
What angle must the wire be at in order for it to work and why
To experience full force the wire has to be at 90 defrees to the magnetic field. If the wire runs along the magnetic field, it won’t experience any force at all
How could you show the direction of force in the motor effect
Apply a current to a set of rails inside a horseshoe magnet
A bar is placed on the rails, which completes the circuit. This generates a force that rolls the bar along the rails
What is the rule that tells you which way the force acts
Flemings left hand rule
Explain how to use Flemings left hand rule
Use your left hand:
Your thuMb will point in the direction of force (Motion)
Your First Finger in the direction of the Field
Your seCond finder in the direction of Current
FFC -ForceFieldCurrent
How do loudspeakers work because of the motor effect
1) A.c electrical signals from an amplifier are fed to a cool of wire in the speaker which is wrapped around the base of a cone
2) the coil surrounded by a permanent magnet, so the ac signals cause a force on the coil and make it move back and forth
3) these movements make the cone vibrate and this creates sounds
What is electromagnetic induction
The creation of a voltage (maybe a current) in a wire which is experiencing a change in magnetic field
What is the Dynamo effect
Using electromagnetic induction to transform kinetic energy into electrical energy
What are the two different situations where you get em induction
1) an electrical conductor (a cool is often used) move through a magnetic field
2) the magnetic field through an electrical conductor changes (gets bigger smaller or reverse)
How do AC generators works
1) generators rotate a school in a magnetic field
2) there construction is presto much like a motor
3) as the coil spins a current is induced in the coil. This current changes direction every half turn
4) instead of a spilt ring commutator AC generators have slip rings and brushes so the contacts don’t swipe every half term
5) this means they produce AC voltage
What do faster revolutions look like and produce in AC generators
Faster revs produce not only more peaks but higher overall voltage. This amplitude is bigger but shorter wavelength
Definition of half life
The time it takes for a radioactive material to lose half of its radioactivity
How do you find pressure difference
Height x density x g
What is an isotope
Isotopes are atoms with different numbers of neutrons but the same number of protons (atomic number)
What are the three kinds of radioactivity
Alpha beta and gamma are three type of ionising radiation
What is radiation by alpha particles
Alpha particles are helium nuclei (4,2 He) alpha particles are made up if 2 protons and 2 neutrons they’re big heavy and slow moving. Therefore don’t penetrated far into materials but are stopped quickly. However are strongly ionising. Because of its electric charge they are deflected by electric and magnetic fields
What is beta particle radiation
Beta particles are electrons (0,-1 e- )
They move quite fast and they are quite small. They penetrate moderately before colliding and are moderately ionising. Because they’re charged (negatively) beta particles are deflected by electric and magnetic a fields
What is gamma ray radiation
Grammar Rays are very short wavelength em waves. They have no mass and are just energy. They are the opposite of alpha particles. Penetrate a long way into materials without being stopped but this means they are weakly in ionising. Gamma rays have no change so they’re not deflected by electric or magnetic fields
Describe and explain Rutherford’s nuclear model of the atom
1) if the plum pudding model was right then alpha particles would just pass through the gold foil
2) the fact that some of the alpha particles bounced back meant that inside the atoms there must be a small positively charge nuclei, which repel the passing alpha particles, so the model of the atom said:
- most of the mass must be concentrated at the centre and most of an atom is empty space
- the nucleus must be small since very few alpha particles are deflected by much.
- it must be positive to repel the positively charged aloha particles
What are the factors that affect the alpha particles in the Rutherford nucleus model of the atom ( graph looking thing)
1) the faster an alpha particles travelling the less it will be deflected by a nucleus
2) the more positively charged a nucleus is (ie the higher the atomic number) the more an alpha particle will be deflected
3) the closer an alpha particle passes to the nucleus the more it will be deflected
Why does the radioactivity of a sample always decrease over time (half life’s)
Each time a decay happens and alpha beta or gamma ray is given out it means one more radioactive nuclei has disappeared
Describe the difference between a short and long half life
A short half life means the activity falls quickly because lots of the nuclei decay quickly.
A long half life means the activity falls more slowly because most of the nuclei don’t decay for a long time - they just sit there unstable
How is half life found from a graph
Find the time interval on the bottom axis corresponding to a halving of the activity in the very axis
What must you always remember to subtract when finding the half life
Measure the background activity first and then subtract it from the every reading you get
What type of waves are sound waves and what causes them
Longitudinal waves caused by vibrating objects. The vibrations are passed through the surrounding medium as a series of compressions
What frequencies is the human ear capable of hearing
Frequencies between 20Hz and 20,000 Hz
How can you measure the speed of sound using two people
You asks friend to stand a long distance away (eg 100m) and bang a drum. Use a stopwatch to measure the time taken between you seeing the person make the noise and when you hear it. Then use the s= d/t to work out the speed
What are the energy transfers in a speaker
Sound->electrical->sound
What are the energy transfers in batteries
Chemical->electrical -> kinetic/heat/light/sound
Describe and explain radiation
All objects are continually emitting and absorbing heat radiation. An object that’s hotter than its surroundings emits more radiation than it absorbs(as it cools down). An object that’s cooler than its surroundings absorbs more radiation than it emits (as it warms up)
Explain conduction of heat
CONDUCTION OF HEAT IS THE PROCESS WHERE VIBRATING PARTICLES PASS ON HEIR EXTRA KINETIC ENERGY TO NEIGHBOURING PARTICLES In a solid the particles are held tightly together. So when one particle vibrates, it collides with other particles nearby and the vibrations quickly pass from particle to particle
Describe and explain convection
Convention occurs when the more energetic particles move from the hotter region to the cooler region and take their heat energy with them
How can you use an experiment to show convention currents working
Use potassium permanganate crystals in the bottle of a beaker of cold water. Then heat it gently over a Bunsen flame. The potassium permanganate starts to dissolve to make a purple solution that gets moved around the beaker by the convection currents as the water heats
What makes gamma radiation sources good for industrial tracers
Strong penetrative power
Weak ionising
Short half life
What is nuclear fission
The splitting of an atom which releases energy
How is nuclear fission used in nuclear power stations
Nuclear power stations are powered by nuclear reactors. In a nuclear reactor, nuclear fission is carried out in a controlled chain reaction. Uranium or plutonium atoms split up releasing loads of energy
How do fission chain reactions work
The fuel that split in a nuclear reactor (and bomb-a nuclear bomb is an uncontrolled fission chain reaction ) is usually uranium-235. If a slow moving neutron gets absorbed by a uranium -235 nucleus. The nucleus can split. Each time U-235 splits up it spits out a number of neutrons. This can go to hit other U-235 nuclei, causing them to split and release even more neutrons which hit even more nuclei and so on. This is known as a chain reaction
What does U-235 split into
It splits in two which will form two new daughter nuclei. These daughter nuclei are lighter elements than uranium
How do control rods in a nuclear reactor limit the rate of fission
They limit the rate of fission by absorbing excess neutrons (often made of boron)
What gas is typically pumped through the reactor and what is its role
Co2 is usually pumped through the reactor to carry away heat generated
What starts the fission process in a nuclear reactor
Free neutrons
What causes the temperature to rise in a nuclear reactor
Atoms produced collide with other atoms causing the temperature in the reactor to rise
What is the role of the moderator in a nuclear restore
The moderator usually graphite or water, slows neutrons so that they can successfully collide with uranium nuclei and sustain the chain reaction
What then happens to the co2 which is pumped through the reactor
The gas is then passed through a heat exchanger, where it gives it energy to water - this water is heated and turned into steam which turns a turbine, which turns a generator generating electricity
