Physics: Radiation For Life
- Created by: William Page-Brown
- Created on: 16-04-13 17:25
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- Physics: radiation for life
- static electricity
- static is caused by friction
- electrons negative
- lack of electrons means positive charge
- opposites attract
- more on static electricity
- disadvantages: attracts dust, clothes cling, shocks from metal
- dangerous if sparks near gases
- earthing allows charge to take easy route
- insulators stop charge reaching you
- uses of static electricity
- paint sprayers opposite charge to car
- dust precipitators, dust attracted to metal plaes
- defibrillators,electricity makes heart contract
- charge in circuits
- current - flow of electrical charge, amps
- voltages - driving force, volts
- resistamnce- slows current, ohms
- broken circuit = no current
- plugs and fuses
- live wire - brown - voltage
- neutral wire - blue - completes circuit
- earth wire - brown and yellow - safety
- anything with non conductive case is double insulated
- fuses melt at high currents
- circuit breaks can be reset
- power = voltage x current
- resistance
- variable resistors can be changed
- resistance increase, current decrease
- longer wires have more resistance
- thinner wires have more resistance
- resistance = voltage / current
- ultrasound treatment and scans
- sound is longitudinal
- made of compression and rare factions
- compressions are high pressure, rarefactions are low pressure
- wavelength - crest to crest
- frequency - complete wavers per second, hertz
- amplitude - middle line to crest, how loud
- ultrasound above 2000Hz: kidney stones, body scanning
- x rays cant see soft tissue and can cause damage
- radioactive decay
- alpha beta gamma
- alpha particle is helium nucleus
- mass and atomic numbers should balance on both sides of nuclear equations
- radioactivity and half life
- as more unstable nuclei decay, radioactivity decrease
- activity never reaches zero
- time taken for half the radioactive nuclei now present to decay
- work out half life in steps
- ionising radiation
- nuclear radiation and x rays are ionising radiation
- ionisation occurs because particles lose or gain electrons
- beta makes atoms negative
- alpha makes atoms positive
- low doses of this mutates and multiplies cells causing cancer
- alpha more dangerous inside body
- gamma and beta more dangerous outside body
- x rays and gamma rays are electromagnetic waves
- medical uses of radiation
- gamma rays focused at tumour
- tracers in medicine with short half lives
- alpha radiation cannot pass through skin and would not be detected
- gamma rays sterilise instruments
- uses of radiation and background radiation
- to find leaks in pipes similar to medical tracers
- a weak alpha source is blocked by smoke particles in a smoke detector
- background radiation comes from: unstable isotopes, cosmic rays, human activity
- radioactive dating
- if a half life is known, radioactive isotopes left can be read
- carbon 14 is used for dating
- nuclear power
- nuclear fission splits atoms releasing heat
- extra neutrons make uranium 235 unstable
- uranium 236 can then divide rapidly
- control rods limit the rate of fission by absorbing neutrons
- nuclear fusion
- joining of atomic nuclei
- doesnt leave much waster
- hard to control or build reactors
- cold fusion would allow us to generate electricity cheaply
- static electricity
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