Use of Electrostatitics...
- Defibrillation is where the hearts regular rhythm is restored.
- A shock from a defibrillator supplies 400 J in a few milliseconds.
- Static electricity is used in paint spraying...
spray gun is charged > all paint particles become charged with the same charge > like charges repel so the particles spread out which makes a fine spray > the object to be painted has the oppisite charge so the particles attract > object gets an even coat with minimal paint wasted.
- If the object being painted is not charged then it still gets painted but: the object becomes charged with the particles meaning further paint droplets are repelled from the object.
- Dust Precipitators are in chimneys of factories and power stations and remove the harmful particles so they don't pollute the atmosphere.
metal grid placed in the chimney with a large negative charge > soot particles leaving become close to the grid they gain a negative charge > like charges repel forcing them onto the positively charged plates
Safe Electicals (First Half)
- electical current = a flow of electic charge.
- Charge is carried by negatively charged electrons and they flow in the oppisite direction to the conventional current.
- ELECTON MOVEMENT...
Electrons are pushed around the circuit > they bumo into atoms which give them energy > there energy makes the atoms vibrate more > the reistor gets hotter > resistance increases.
- A variable resistor changes the resistance
- The difference in voltage between 2 points is called the potential difference.
Fixed Resistor = potential difference across it increases, the current decreases.
Fixed Power Supply = as the resistance increases, the current decreases.
Safe Electricals (Second Half)
LIVE WIRE - Carries a high voltage around the house.
NEUTRAL WIRE - Completes the circuit, return path for the current.
EARTH WIRE - Connected to the casing of something to stop it being live.
-If a circuit becomes too large, the fuse contains a wire which melts breaking the circuit.
-Current can't flow, which stops overheating and damage to the appliance.
-Fuses stop a person recieving an electric shock because as soon as the casing becomes live, a large current flowws in the earth and live wires and the fuse 'blows'.
-A circuit breaker (re-settable fuse) doesn't need to be replaced, it can just be reset.
Atom? This is a positively charged nucleus surrounded by an equal number of negatively charged electrons.
ELECTROSTATIC effects are due to electron movement.
A stable neutral atom there are equal amounts of positive/negative charge.
Like charges repel, unlike charges attract.
- Polythene rod + rubbed with a duster = electrons transferred to polythene = polythene rod negatively charged.
- Acetate rod + rubber with a duster = electrons transferred to the duster = acetate positively charged.
GENERAL RULE... and object as a:
- a negative charge because its got gained electrons
- a positive charge because its lost electrons