Physics Summary Questions

1)What is Specific heat capacity?
the amount of energy needed to raise the temperature of 1g of substance by 1°C. J/Kg/°C
5)Briefly describe how heat is transferred through a)conduction, b)convection and c)radiation
a)Vibrating particles pass on extra kinetic energy to neighbouring particles
b)More energetic particles move from the hotter region to the cooler region-taking heat energy with them
c)Heat radiated as IR waves. Doesn't need medium, occurs through transparent substances and amount of radiation depends on surface colour and texture
6)Describe how heat radiaiton is used to cook food under a grill, and in a microwave oven
Grill-Heat absorbed by surface particles (increasing KE) and is conducted or convected to the centre.
Microwave oven-Penetrate 1cm into the outer layer of food. Absorbed by water and fat particles which increases KE. Energy is conducted or convected to the centre of the food
7)Describe three ways of saving energy in the home and explain how each one works
-Loft Insulation-Fibreglass wool reduces conduction
-Cavity Walls & insulation-Two layers of brick with gap between reduces conduction . Squirt insulating foam into gap traps pockets of air to minimise convection
-Double Glazing-Two layers of glass with air gap reduces conduction

12)Briefly describe what happens to wave when it is a)diffracted, b)refracted
a)The wave spreads out at the edges
b)The speed changes and may change direction
13)List the seven types of em wave in order of wavelength (smallest 2 largest)
Gamma, X-ray, UV, Visible, IR, MW, RW
14)Explain why Morse code is  a digital signal
It uses light pulses which is either 'on' or 'off'
15)Describe how light signals can travel through optical fibres
Ray of light enters fibre greater than critical angle. Causes total internal reflection and reflected again and again
16)Explain the properties if laser beams which make them a)monochromatic, b)coherent
a)All the waves are at the same frequency
b)Fixed phase difference
17)Describe how lasers are used in CD players
A laser shone is reflected from shiny bottom surface. Beam reflected from land and pit slightly differently-picked up by light sensor. Changed into electrical signal

18)Briefly explain how IR is used to control electircal equipment
Remote control emit pulses of IR. Pulses act as digital code and device detects and decodes, following the coded instruction
19)Explain why long-wave radio waves can bend around obstacles
They diffract aroiund the curved surface of the Earth
20)Briefly describe what happens to radio waves in the ionosphere
Short-wave signals reflect off the ionosphere
22)Describe how satellites are used for communication
Use microwaves that pass easily through wuatery atmosphere without too much absorption. Signal from transmitter transmitted to reciever dish orbiting and transmits back where it's recieved from satellite dish.
23)Why are microwave transmitters located in high places and close together?
Microwaves have a shorter wavelength so don't diffract much so affected by curvature of the Earth. Also, blocked by large obstacles
25)Explain how diffraction affects the size of reciever needed to pick up different wave signals
The minimum size of reciever needed is linked to size of wavelength of wave
26)Explain the difference between analogue and digital signals
A-Take any value within certain range-Continuous, D-Only take 2 values-On/off-discontinuous

2)Explain how wind turbines convert energy from the sun into electiricty
Sun heats air which causes convection currents. Turbines are turned by this air movement & convert their KE into electrical energy (blades turn a generator
3)Briefly describe how a typical power station works
Fuel is burned, Boils water, Generates steam, Steam turns turbine, Turbine generates electricity via electromagnetic induction
4)Give one advantage and one disadvantage of using
a) fossil fuels-Readily available, lots of energy, We are running out
b)biomass, to generate power-Renewable, Lots of biomass is needed to replace one lump of coal
5)Define em induction. what factors affect the size of the induced voltage and current?
The creation of a voltage in a wire which is experiencing a change in magnetic field. Strength of the amgnet, no of turns on coil, speed of movement
6)Describe how a generator works
Generators rotate a coil in a magnetic field. Every half turn the current swaps direction

7)Explain why a very high electrical voltage is used to transmit electricity in the national gird
So lower current can be used which decreases resistance (energy lost through heat) and same power can be attained of the volatge is high and current is low because power=voltage x current
9)a)How many units of electiricty (in KWh) would a kettle of power 2500 W use in 3 mins?
   b)How much would that cost, if one unit of electiricy costs 12p?
10)Briefly describe how the greenhouse effect keeps the earth warm
Some wavelengths pass through the atmosphere and are absorbed by the Earth's surface which then emits this radiation as a longer wavelength
This IR is absorbed by CO2, water vapour & methane in the air which emit heat in all directions, including back to Earth
Atmosphere acts as an insulating layer - stopping Earth from losing all its heat at night
11)How has human acitivity affected weather patterns?
Burning fuels, Cattle farming, Decaying waste in land fill, Rising CO2 levels from humans
These all release greenhouse gases, Soot produced by factories reflects heat from cities back down to earth - increasing local temperature

13)Explain which types of nuclear radiation are used, and why, in each of the following:
a)medical tracers-Beta or gamma is used as it passes through the body
b)treating cancer-Because high doses of gamma rays will kill cells
By directing it at the cancer in the right dosage it kills the cancer cells but does not damage too many normal ones
c)smoke detectors-Alpha radiation ionises air particles
-smoke particles hit by alpha radiation
- less ionisation of air particles
- current is reduced causing alarm to sound.
14)Give one advantage and one disadvantage of nuclear power
A-Lots of energy without releasing lots of CO2, D-Processing the uranium before use causes pollution
15)Describe the precautions you should take when handling radioactive sources in the laboratory
Need to be stored safely, kept in labelled lead box, keep exposure time short, handle with tongs, keep at arms length, avoid looking directly

16)Briefly explain why it's difficult to dispose of high-level radioactive waste safely
Must be geologically stable - earthquakes can could canister to leak material, if it gets into ground water then it could contaminate plants & get into drinking water
People often object to it being buried near them so most high-level waste is kept on-site
Waste can be reprocessed to retrieve some useful material
Nuclear power plants must be secure to stop terrorists from stealing dangerous materials or attacking the station
There are strict regulations as to how this waste is disposed of, these rules change depending on new studies / research
17)What shape are the orbits of the planets in the solar system?
Elliptical
18)What forces keeps planets and satellites in their orbits?
gravitational force that provides the centripetal force that acts on the centre of the object for circular motions
19)What are asteroids and where are they found? How are they different to meteorites?
Made of rubble and rock and found between orbits of Jupiter and Mars. Different to meteorites because they haven't crashed down to earth

20)Briefly describe evidence that led scientists to think that moon may be result of another planet colliding with Earth
Moons had lower density than Earth, doesn't have big iron core, Moon rocks contain few substances which evaporate at low temp-moon formed from hot material
22)Briefly describe the problems with sending a group of astronauts to Neptune
Carry lots of food, water and oxygen. Regulate temp and removed toxic gases. Shield astronauts from radiation. Low gravity causes muscle wastage and loss of bone tissue
23)Give 2 advantages and 2 disadvantages of unmanned space travel
A-Withstand conditions lethal to humans, If crashes no one is hurt. D-Can't think for themselves, Can't do maintenance and repairs
25)Briefly describe the 'Big Bang' theory for the origin of the universe
All the matter in the Universe originally occupied a very small place, it then 'exploded' into the Universe we see today
26)List the steps that lead to the formation of a main sequence star
Stars form form clouds of dust and gas, gravitational collapse producing a protostar, thermo nuclear fusion- produced heat provides outward pressure to balance force of gravity, long period of normal life (mainsequence)
28)Explain the evidence that Galileo produced that supported Copernicus' theory
Galileo showed that Jupiter had moons (they disappeared behind it sometimes) - this showed that not everything orbited the Earth

5)Explain the difference between mass and weight. What's the formula for weight?
Mass is the amoutn of stuff in an object, Weight is caused by the pull of gravity.                              Weight =mass*Gravitational field strength
7)Describe the effect on the top speed of a car of adding a roof box. Explain your answer
Roof boxes spoil the shape and slow them down because it increases drag
13)List all the factors which affect each of the 2 parts of the stopping distance
Thinking Distance-How fast you're going, How dopey you are (Tiredness, Drugs, Distractions)
Braking Distance-How fast you're going, How heavily loaded the vehicle is, How good your brakes are (worn or faulty), How good the grip is (road surface-leaves and diesel spills, weather-wet or icy roads, Tyres-Bald tyres)
18)Explain how seat belts, crumple zones and air bags are useful in a crash
Seat Belts-Increasing the time so reduces forces, Crumple Zones-change shpae increasing time, Air Bags- slow you down gradually
19)How do ABS brakes make driving safer?
They automatically pump on and off to prevent skidding and give shorter braking distance
23)How does the KE formula explain the effect of speed on the stopping distance of a car?
Braking distance increases as speed squared increases so increases stopping distance

29)Give 3 factors that affect the fuel consumption of a car
Driving style-faster accelerations, frequent braking, different road conditions, Work against friction-openign windows, roof box increases air resistance and drag, Mass of the car
30)Electric vehicles don't give out polluting gases directly, but they still cause pollution. Explain why
Batteries need to be charged using electricity from power stations

1)What causes static charge to build up?
Friction- Two insulating materials are rubbed together, electrons will be scraped off one and dumped on the other. Leaves a +ve static charge on one due to lack of electrons-it lost electrons
3)Give 2 examples each of static electricity being:
a)nuisance-Shocks from door handles-if you walk on a nylon carpet wearing shoes with insulating soles, charge builds up.Then if you touch a metal door handle or water pipe the charge flows via conductor
b)dangerous-A lot of charge can build up on clothes-large static charge builds up on synthetic materials if they rub. large enough to make a spark
5)Give 3 examples of how static electiricty can be helpful. Write all the details
-Paint sprayers-Electrostatic paint sprayers are charged. Each paint drop repels so a fine spray. Object is given opposite charge so attracts fine spray. Gives even coat and shadows are painted
-Dust Precipitators-high voltage metal grids put into chimneys to produce a charge on the dust
• dust particles gain or lose electrons
• dust particles induce opposite charge on earthed metal plates
• dust particles are attracted to the plates

7)Describe what earthing and double insulation are. Why are they useful?
Earthing-Metal cases must be attached to earth wire, Double insulation-Has casing that's non-conductive. Both reduce electric shock
10)Explain how you could work out the resistance of a resistor in a circuit
R=V/C
11)Define the frequency, wavelengh and amplitude of a wave
Frequency-How many complete waves per second, Wavelength-Full cycle of a wave, Amplitude-How much energy wave is carrying
15)Give a proper definition of a half-life
The time taken for half o the radioactive nuclei now present to decay
17)Why are alpha particles so good at ionising atoms?
Relatively large so collide with other atoms easily and highly charge so can easily remove electrons when passing and colliding with atoms
18)What is the main difference between X-rays and gamma rays?
-both are ionising electromagnetic waves
-both have similar wavelengths
-x-rays are easier to control, created by firing high speed electrons at metal targets
-gamma rays are released from the nucleus of radioactive materials

19)Describe in detail how radioactive sources are used in each of the following:
a)treating cancer-Gamma rays focused on tumour with wide, rotataing beam and taking care to not damage (ionise) non-cancerous cells
b)tracers in medicine-Gamma or beta with short half-life ingested/drunk/eaten/injected into body and allowed to spread. Followed by radiation detector
20)Describe in detail how radioactive sources are used in each of the following:
a)tracers in industry-Squirt radioactive isotope then go along with detector. if reduces or stops then leak or blockages.
b)smoke alarms-Weak alpha radioactive isotope placed close to two electrodes. Causes ionisation which allows current to flow. Smoke particles hit by alpha particles. Causes less ionisation so current reduced and alarm sounds
22)What type of particles is uranium-235 bombarded with in a nuclear reactor to make it split?
Slow-moving neutrons
23)Explain how a chain reaction is created in a nuclear reactor
Neutrons released from previous fissions to hit other U-235. Each split one releases more than one neutron. Cause further nuclei to split-chain reaction

P4.4

24)What is the difference between nuclear fission and nuclear fusion?
Nuclear Fission-Splitting up of Uranium atoms, Nuclear Fusion-Joining of small light atomic nuclei
25)Briefly explain why cold fusion isn't accepted as a realistic method of energy production
Scientists are unable to replicate the same results as those who claimed cold fusion worked. The results achieved were unreliable

1)What's the difference between speed and velocity? Give an example of each
Speed-how fast-direction not important e.g 30mph, Velocity-speed and direction e.g 30mph due north
8)Briefly describe Newton's third law and use it to explain recoil
If object A exerts a force on object B, then object B exerts an equal but opposite force on object A. When gun is fired, bullet exerts force on gun. so bullet travels out of barrel and gun recoils in oppotisite direction
10a)What happens to the pressure of a gas if: the volume of the gas increases
Pressure decreases
12)State three differences between a low polar orbit and a geostationary orbit
Low polar-both poles whilst Earth rotates beneath, period of 2 hours, closer to Earth
Geostationary-High orbit, over equator, period of 24 hours
14)Briefly explain why satellite transmitting and recieving dishes need careful allignment
Wavelength of MW is too short for aerials so satellite uses a dish. Dish very large so MW doesn't diffract much-produces narrow beam
17)What effect does a polarising filter have on the light passing through it
it ransmits vibrations in one direction only

22)What is a real image? How is it different from a virtual image?
Real image-light from an object comes together to form image on screen
Virtual-rays diverging so light from object appears to be comign from different place

1)Briefly explain what causes resistance in a metal conductor
Electrons collide with atoms in metal. Collisions cause atoms to vibrate increasing resistance
5)Explain how potential dividers work
Consist of pair of resistors. Divide potential ina circuit so you can get output of different voltages
13)Give a definition of a magnetic field
A region where magnetic materials and also wires carryign currents experience a force acting on them
16)Explain how Fleming's Left-Hand rule work
It tells you which way the force acts. First finger-Field, Second finger- Current, Thumb-Motion
18)What is em induction? List 4 factors which affect the size of the induced voltage
Creation of a voltage in a wire which is experiencing a chaneg in magnetic field. Strength of magent, number of turns on coil, Area of coil, speed of movement
23) Explain why power transmitted at such a high voltage
To transmit a lot of power. High current is the loss due to the resistance of the cables. Cheaper to boost up voltage and keeps current low.

24)Write down 3 facts about isolating transformers
They have equal turns of primary and secondary coils. Found in mains circuits in the home. For safety  and prevents a physical connection so minimises risk of live parts touching earth and minimises risk of getting electrocuted
25) Explain briefly how a diode works. What semiconducting material are diodes often made of?
Diode only lets current flow in one direction. Silicon.
27) What is a capacitor? How can it be used to smooth rectified voltage?
Store charge. Adding in parallel with output device