Hard Content :( Flashcards by amandine meertens

Define planet:

A natural object that orbits the sun. Must be spherical and be in its own orbit.

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Define moon:

natural object that orbits a planet

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Define Oort Cloud:

Region of icy particles on outside of our solar system

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Define comet:

made of ice and dust, came from the edge of our solar system

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Define universe:

a collection of galaxies

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If a main sequence star has a larger mass than the sun what will happen to it?

super red giant, supernova +black hole -neutron star

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If a main sequence star has a mass similar to the sun, what will happen to it?

red giant, white dwarf, red/black dwarf

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How does a main sequence star turn into a red/super red giant?

Runs out of hydrogen fuel so begins to fuse helium, causing star to collapse and start dying

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How is a white dwarf formed?

No more fusion occurs in red/super red giant because helium is used up. star begins to collapse and die.

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How is a black/red dwarf formed?

when white dwarf no longer has energy it cools and eventually turns black

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How is a supernova formed?

when a super red giant runs out of fuel it begins to collapse but because the star is so big it will implode and radiate matter into the galaxy

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How is a neutron star formed?

If there is little mass left after supernova, all protons and electrons collapse to form neutrons

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How is a black hole formed?

If there is high mass, star continues to collapse until it reaches zero volume

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What colour is a celestial object if it is moving towards you?

blue

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What rule is used for electromagnetic induction?

right hand rule - thumb is force, index is magnetic field direction and middle is conventional current

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What is CMBR?

radiation from the Big Bang that has been stretched and is now present in our surroundings

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What is the equation for red shift calculations?

observed wavelength/original wavelength = recessional velocity/speed of light

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Define the Doppler effect:

When the apparent wavelength and frequency changes due to the movement of the source towards or away from an observer

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How is red shift of galaxies proof of the Big Bang?

red shift of galaxies shows that all galaxies are moving away from each other
this implies they are expanding
the further away, the faster the galaxies are moving
all galaxies have been moving away from us for the same amount of time so they must have started in the same place

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What is voltage?

the energy transferred per unit charge

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What is the equation linking current, charge and time?

current = charge/time

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Define charging by friction:

apply frictional force between two insulators creating ‘permanent charge’

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What is Ohm’s law?

ohm’s law states that the voltage and current are proportional for a component where there is a fixed resistance

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How does temperature affect resistance?

higher resistance as ions vibrate more as they have more kinetic energy, increasing the collisions

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What is a conductor?

delocalised electrons

What is an insulator?

localised electrons

Define power in an electricity context:

rate of energy tranfer

What colour is the live wire?

brown

What colour is the neutral wire?

blue

What is the first gas law?

the temperature is proportional to the pressure when there is a constant volume and number of particles

What is the equation linking pressure and temperature?

P1/T1=P2/T2

What is Boyle's law?

pressure and volume are inversely proportional when the temperature and number of particles is constant

What is the equation linking pressure and volume?

P1V1=P2V2

What is work done?

the mechanical energy transfer

How can you calculate work done?

work done = force x distance

What is the equation linking energy transferred, power and time?

power = energy transferred/time

Define power in an energy context:

the rate of energy transfer

What are the four energy transfers?

by heating, by radiation, mechanically, electrically

What are the 8 energy stores?

mechanical, elastic, gravitational, chemical, kinetic, nuclear, electrostatic, magnetic

How can you calculate GPE?

height x g x mass

How can you calculate kinetic energy?

0.5 x mass x velocity squared

What is kinetic energy?

the energy stored in an object when it is moving at a constant speed

What is gravitational potential energy?

the energy stored in an object if it is raised above the ground

State Hooke's law:

To obey Hooke's law the force must be proportional to the extension

What is the elastic limit?

the force applied where an object changes from elastic to plastic

What is terminal velocity?

when the weight of an object is balanced with its air resistance

Is 'v' final speed or initial speed?

final speed

Is 'u' final speed of initial speed?

initial speed

What is contamination (radioactivity)?

when a radioactive substance has been absorbed into an object and now emits the radiation itself

What is irradiation?

when an object has been exposed to radiation, but it has not absorbed it and does not emit it itself

What is the mass and atomic number of beta?

mass = 0 atomic = -1

What is the mass and atomic number of alpha?

mass = 4 atomic = 2

Define activity:

a measure of the number of decays per second

What is the nature of alpha?

2 protons and 2 neutrons

How does a tracer work?

gamma is attached to a molecule that is absorbed in the body by tutors and growths.

How does a smoke detector work?

alpha source ionises air making it positive, it then travels to negative plate. smoke absorbs alpha particles, no alpha detected at negative plate, alarm

What are 5 sources of background radiation?

radon from ground, cosmic rays, artificial, food and drink, buildings

What is background radiation due to?

the natural decay of unstable nuclei in our surroundings

Define nuclear fission:

induced nuclear fission is when a slow moving neutron is injected into a large unstable nucleus, splitting it into 2 or 3 neutrons and 2 daughter nuclei

Define nuclear fusion:

when two small nuclei join together to make one large nucleus

What are moderators used for?

to slow down neutrons

What are control rods used for?

absorbs neutrons to control the rate

Field lines run from.... to .....

north to south

What are three ways to align domains?

1. bring permanent magnet close to material 2. apply force 3. electromagnet

What rule is used for magnetic fields around current carrying wires?

right hand thumb rule. thumb = conventional current, fingers = magnetic field

what rule is used for magnetic fields through solenoids?

right hand thumb rule. thumb = north, fingers = direction of current in wire

how can you increase the strength of an electromagnet?

more coils, higher current, change material of core

What happens when a current carrying wire is placed in a magnetic field?

magnetic fields interact creating force and motion

what rule is used when a current carrying wire is placed in a magnetic field?

Fleming's left hand rule

What is Fleming's left hand rule?

thumb = force, index = magnetic field, middle = conventional current

How can you create a larger force when a current carrying wire is placed in a magnetic field?

increase current, increase strength of magnet, longer wire

How does a DC motor work?

circuit is connected, flows in opposite directions in coil, producing opposing forces, rotating coil, at vertical position, commutator is no longer connected to the brushes, so no current flows, but momentum keeps in rotating, commutator reconnects with brushes and current flows again

how can you increase the speed of a DC motor?

increase current, increase magnetic field strength, increase number of turns on coil, increase area of coil

how does electromagnetic induction work?

bar magnet cuts solenoid, inducing a current and voltage

How can you predict the direction of current in electromagnetic induction?

right hand rule. thumb = force, index = magnetic field, middle = conventional current

What is the purpose of a transformer?

to change the voltage of a power supply

How does a transformer work?

alternating current in primary coil produces alternating magnetic field which permeates through the core. magnetic field cuts secondary coil inducing a voltage and current

what is the relationship between number of turns and voltage?

Vp/Turnsp = Vs/Turnss

what is the relationship between primary and secondary power?

VpIp=VsIs