p4

• Created by: Katie
• Created on: 28-11-11 21:10

## 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

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## 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.

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## 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.

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## Sparks! 1

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
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