P2.23456 Flashcards
What is the same as work done
Work done (j) = energy transferred )j)
What is work done mainly transferred into against frictional forces
Heat energy
What energy is stored in the object when work is done to change its shape
Elastic potential energy
What is kinetic energy
What is it dependent on
The energy an object has because of its movement
The mass of the object
The speed of the object
Steps of a pendulum swinging
Before its released it has gravitational potential energy but no kinetic energy
When it swings downward, the GPE coverts into kinetic energy
The pendulum swings back upwards and converts all the kinetic energy to GPE
The pendulum comes to a stop for a moment as it changes direction
It then swings back down and the energy is transferred to kinetic energy again
What would happen if there was no resistant forces in the pendulum process
What happen when there are resistive forces
It would keep repeating forever
Some energy is used to overcome the resistive force, producing heat. The pendulum comes to a halt after all it’s energy has been transferred into the surroundings as heat
What is momentum
What does it depend on
The measure of the state of motion of an object
The mass of the object
The velocity of the object
Examples of safety precautions and breaking precautions in cars
Seat belts- they exert a force to counteract the momentum of the person wearing them
Crumple zone- an area of a car designed to crumple on impact and absorb some of the kinetic energy of the crash. Instead of coming to an immediate halt there will be more time during which the momentum is reduced
Air bags- distribute the force of impact more evenly over the upper body area and reduce the momentum of the body more gradually
What are regenerative brakes better than friction brakes
Regenerative braking transfers the kinetic energy of the vehicle to electrical energy. In electric vehicles this is used to recharge the batteries and increases the overall efficiency of the vehicle because this energy can be reused rather than lost as heat to the surroundings
What happens with electrons in static electricity
Static builds up when electrons (which have a negative charge) are rubbed off one material into another. The material receiving the electrons become negatively charged and the one giving up electrons becomes positively charged
What happens when two materials with the same type of charge are brought together
What happens when two materials with different types of charge are brought together
They repeal each other
They attract each other
What substances allow electrical charge to flow easily through them
Conductors
What is electrical current
What does the amount of current flowing depend on
The flow of charge
The resistance of the bulb and the potential difference
What does the potential difference tell us
How much work is done
What does a bigger potential difference produce
A bigger current and more energy
What does a good conductor have
A larger number of free electrons so has a lower resistance
What is potential difference measured in? How is it measured?
What is current measured in? How is it measured?
Measured in volts using a voltmeter
Measured in amps using an ammeter
What is resistance
A measure of how hard it is to get a current through a component at a particular potential difference
How does potential difference work in a series circuit
The PD supplied by the battery is divided up between the components in the circuit
How does potential difference work in a parallel circuit
The potential difference across each component is the same
What is a direct current like
What is alternating current like
It always flows in the same direction
It changes direction of flow back and forth continuously
What is the uks main supply voltage
230 volts
What are the inner cores of wires made of? Why?
What are the outer layers of wires made of? Why?
What are the pins of a plug made of? Why?
What are some appliances double insulated
Copper because it’s a good conductor
Flexible plastic because it is a good insulator
Brass because it’s a good conductor
So if there is only a singular fault it doesn’t lead to an exposed live connection
What is a residual current circuit breaker
A device that automatically breaks an electric circuit if the circuit becomes overloaded
When a RCCB detects a fault it trips a switch to break the circuit much quicker than a fuse would. This makes an RCCB better at protecting users
How do earth wires work
The outer case of an appliance is connected to the earth pin in the plug by the earth wire
If a fault in the appliance connects the live wire to the case, the case will become live. The current will then flow to earth through the earth wire because this offers least resistance
This overload of current will cause the fuse to melt, or the circuit breaker to trip
What is an electric charge
What does it do
The rate of flow of charge
It transfers electrical energy from a battery or power supply to components in a circuit
What does a resistor do
Transfers electrical energy into heat energy. The rate at which energy is transferred in a device is called the power
What is the connection between potential difference and energy transfer
The greater the potential difference, the more energy transferred by every coulomb of charge
Safety precautions with sockets
Electrical sockets are not allowed in bathrooms and should not be situated close to water supplies
Connecting multi- sockets extension leads together can overload the electrical system (if the fuse doesn’t work properly) could result in a fire
What should you consider when choosing cables for different cables
The cable should be able to carry the maximum current without heating up
What are the three parts of an atom
Protons
Neutrons
Electrons
What is the mass number
What is the atomic number
The total number of protons and neutrons in an atom
The number of protons in an atom
What is an isotope
Atoms do the same element with different numbers of neutrons
What substances give out radiation from the nuclei of their atoms all the time
Radioactive substances
What are the three types of radiation
Alpha- an alpha particle is a helium nucleus
Beta- beta particle is a high energy electron that is injected from the nucleus
Gamma- high frequency electromagnetic radiation
What absorbs alpha
What absorbs beta
What absorbs gamma
Paper
Aluminium
Lead
What are alpha and beta rays deflected by
Why?
Why are gamma rays not deflected?
Electric and magnetic fields because they are composed of charged particles
Because it is not made up of charged particles
Why are alpha particles deflected less than beta particles
Because they are heavier
They are deflected in the opposite direction because their charge is the opposition of beta particles
What are the 3 uses of radiation
Sterilisation- gamma rays can be used to sterilise medical instruments and food because they kill bacteria
Treating cancer- gamma rays can be used to kill cancerous cell
Controlling the thickness materials- the greater the thickness of the material, the greater the absorption of radiation. This can be used to control the thickness of some manufactured materials e.g. Paper
How is radiation used in paper production
If the paper is too thick then less radiation passes through to the detector, and a signal is sent to the rollers which move closer together
What can cause cancer
Damage to cells is organs
The larger the dose of radiation the greater the risk of cancer
Why does alpha radiation cause the most damage
Because alpha radiation is easily absorbed by cells causing the most ionisation. Whereas beta and gamma radiation are less likely to be absorbed so cause less damage
What does the half life of a radioactive isotope do
It provides information about the rate of radioactive decay
What information does the half life provide
The average time it takes for the number of nuclei of the isotope in a sample to halve
The average time it takes for the for the count rate of a sample containing the isotope to halve
What are radioactive isotopes
Atoms with unstable nuclei that will eventually disintegrate and emit radiation
How does alpha decay work
The original atom decays by ejecting an alpha particle from the nucleus. This particle is a helium nucleus. A new atom is formed after alpha decay
How does beta decay work
The original atom decay by changing a neutron into a proton and an electron. This high energy electron, which is now ejected from the nucleus, is a beta particle. A new atom is formed after beta decay
What is nuclear fusion
The joining together of two or more atomic nuclei to form a larger atomic nucleus. It takes a very high temperature to force the nuclei to fuse
It generally releases more energy than it uses which makes it self sustaining
What is an example of nuclear fusion
The fusion of two heavy forms of hydrogen (deuterium and tritium)
What is nuclear fission
The process of splitting large atomic nuclei. It is used in nuclear reactors to produce energy to make electricity. For fusion to occur the nucleus must first absorb a neutron. When fission occurs the nucleus splits into two smaller nuclei emitting two or three neutrons and releasing energy. The neutrons released can be absorbed by another uranium nucleus and cause a chain reaction
How are stars formed
Gravitational attraction pulls clouds of gas and dust together to form a protostar. As this mass comes together it becomes hotter. Soon it becomes hot enough for hydrogen to fuse to form helium and a star is formed. This nuclear fusion releases massive amounts of energy and produces all the naturally occurring elements. Dust may also clump together to form larger masses and eventually planets
How does a star remain stable
Balance of forces within it- radiation pressure of fusion and force of gravity equal long each other out
What happens to a star the size of our sun at the end of its life
It will expand to be on a red giant
The red giant then cools down and collapses under its own gravity to become a white dwarf
A white dwarf slowly cools to become a black dwarf
What happens to a star much bigger than our sun at the end of its life
It expands enormously to become red supergiants
The red supergiant then shrinks rapidly and explodes, releasing massive amounts of energy, dust and gas into space. This is called supernova. The remains the form a neutron star. This is the core of the star that remains after the explosion. A neutron star is made only of neutrons and is very dense
How are black holes formed
What are they like
When the largest neutron stars collapse further
They are so dense that nothing can escape from their very strong gravitational field- not even light
