P4- Radiation for Life

• when materials rub together, subatomic particles (electrons) transfer to the object being rubbed on
• if you lose electrons you become positive
• if you gain electrons you become negative
• opposite charges attract, same charges repel 

to reduce the chance of getting a shock you can:

• earth the applience
• use insulation mats
• wear shoes with insulating soles
• bond fuel tanks to aircrafts

static electrisity can be a nuisance:

• TV screens becoming charged atrracting dust
• synthetic clothes cling to body

An anti-static line connects objects so they are connected to earth.

• metal plates are connected to a high voltage so have a large potential difference
• the grid and plates are oppositly charged
• waste gases pass through the grid and gain a charge, they are then attracted to the plates

• paint is attracted to the car
• paint repels eachother so spreads out
• when an area is painted it no longer attracts the paint
• paint is attracted to all surfaces so front and back is painted. 
• pros:
• give car a more professional finish
• less paint is wasted
• quicker than normal work

• X-rays are produced by firing high speed electrons at an angled metal target
• gamma is emmitted from the nuclei of some radio active atoms
• X-rays can be dangerous if you have a high enough dosage
• Gamma is the most penetrating so is harmful to cells and can cause cancer
• In hospital X-rays can produce images
• Gamma is used for radio therapy (gamma knife) + tracers & to sterlilise medical equipment 
• Gamma knife focuses gamma onto cancerous cells. it rotates around the point giving a full dose to the cancerous cell & low doses to the surrounding areas 
• tracers are made with short half life gamma. They are drunk or injected. A special cammera films movement of fluid in the body finding leaks.
• Both X-rays and gamma rays are elecromganetic waves
• an x-ray machine can be turned off but gamma is a constant production

useful video:

https://www.youtube.com/watch?v=n6hj-jWpXfo

Nuclear Fusion - fusing together of hydrogen neuclei resulting in the fromation of helium

• producing this reaction on Earth is difficult due to the conditions needed
• conditions- exstremly high temerature & high pressure
• this reaction occurs naturally in stars 
• some scientist have reported carrying out reactions at normal conditions, while others couldn't 
• if cold fusion works, it would mean cheap, limitless electricity

• Nuclear power stations work the same as fossil fuel stations but with uranium as the fuel
• heat is produced in a reactor due to uranium decay causing a chain reaction
• a single neutron causes uranium to split causing heat and new neutrons to be produced
• radioactive waste is produced 
• https://www.youtube.com/watch?v=MGj_aJz7cTs

• ultrasound is a longatudinal wave
• it has a high frequency & short wave length meaning it can penetrate the human body

we can use ultrasound instead of x-rays because:

• it produces images of soft tissue
• it doesn't damage living cells

uses of ultrasound:

• body scans
• shatter kidney stones
• measure blood flow due to the doppler effect

• radio active carbon can be used to date things
• radiation comes from rocks and soil
• older the rock, lower the uranium:lead ratio 
• younger the rocks higher the uranium:lead ratio, this is how we date the earth

Alpha:

• nucleus of a helium atom
• charge of 2+
• it is unstable due to neutrons

Beta:

• its a high energy fast moving electron
• its is less ionising
• its is stopped by a sheet of aluminium

Gamma:

• it has no charge
• emitted at the same time as alpha or beta
• it is stopped by concrete or lead

radiation collides with neutral atoms, altering structureby knocking off electron making them ions, when DNA is ionised, the chemical reactions stop causing cancer.

half life- amount of time taken for half of the atom in a sample to decay

activity- number of nuclear decays emitted per second 

• live wire - brown - carries high voltage
• neutral - blue - completes circuit
• Earth - yellow & green - prevents applience becoming live, if the live wire becomes lose & touches case, earth wire passes down current causing a surge and melting the fuse
• cases can sometimes be double insulated - a plastic coat to prvent appliance becoming live

• current - flow of electron
• voltage - amount of energy transfered
• resistance - removes energy from electrons & slows them down
• voltage = current x resistance
• "the current flowing through a wire is proportional to the potential difference (voltage) across it providing temperature remains constant" - Ohm's law 

pros of circuit breakers rather than fuses:

• switch current off faster & detect smaller charges
• easily reset & reused