The chance of getting an electric shock can be reduced by : 1) correct earthing. 2) standing on insulating mats. 3) wearing shoes with insulating soles. 4) bonding fuel tanker to aircraft
Electrostatic effects are caused by the transfer of electrons
A positively charged object lacks electrons
A negatively charged object has extra electrons
Like charges repel
Unlike charges attract
Uses of electrostatics include : defribrillators, paint and crop sprayers, dust precipitators, and photocopiers
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USING ELECTRICITY SAFELY
In a three pin plug : 1) live wire is at high voltage. 2) neutral wire completes the circuit. 3) earth wire is connected to the case to prevent it becoming live.
Double insulated appliances do not need an earth wire
power = voltage x current
The fuse (or circuit breaker) is in the live wire. If the current is greater than the rating, the fuse will melt (or circuit breaker break), breaking the circuit
resistance = voltage / current
Longer wires have more resistance
Thinner wires have more resistance
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ULTRASOUND
Medical uses include : 1) scans to see inside the body without surgery. 2) measuring the rate of blood flow. 3) breaking up kidney stones
Ultrasound is above 20,000 Hz which is a higher frequency than humans can hear
Longitudinal waves - e.g. sound and ultrasound
Transverse waves - e.g. light
Wavelength is the distance occupied by one complete wave
Frequency is the number of complete waves in one second
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NUCLEAR RADIATION
Gamma rays are given out from the nucleus of certain radioactive materials
X-Rays are made by firing high speed electrons at a metal target
Nuclear radiation is emitted from the nucleii of radioisotopes : 1) alpha particle is a helium nucleus. 2) beta particle is a fast-moving electron. 3) gamma radiation is a short wavelength electromagnetic wave
Fission is the splitting up of a large nucleus
Fusion is the joining together of smaller nucleii
Both release a lot of energy
Fission is currently used to generate electricity
Fission leads to a chain reaction which must be carefully controlled
Medical uses include : 1) diagnosis, as a tracer. 2) sterilising equipment. 3) treating cancers
Other used include : 1) smoke detectors. 2) industrial tracers. 3) dating rocks and archaeological finds
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