Physics

P4-

An atom consists of a small positively charged nucleus surrounded by an equal number of negative charged electrons.

In a stable neutral atom there are the same amount of positive and negative charges. When are polythene rod is rubbed with a duster, electrons are transferred from the duster to the polythene, making the road negative.

When an acetate rod is rubbed with the duster, electrons are transferred from the acetate to the duster, leaving the rod positively charged.

When in flammable gases or vapour is a present or there is a high concentration of oxygen spark from static electricity could ignite the gas or the vapours and cause an explosion. If a person touches something at a high voltage, large amounts of electric charge may flow through the body to Earth.

Dust and dirt are attracted to insulators, such as television screens. Clothes made from synthetic materials often 'cling' to each other and to the body. The  dust precipitator removes harmful particles from the chimneys of factories and power stations are pollute the atmosphere.

-A metal grid is placed in the chimney and given a large charge from a high voltage supply.

-As the dust particles pass close to the grid, they become charged with the same charge as the grid.

-Like charges repel, so the dust particles are repelled away from the wires.

-They are attracted to the opposite they charge plates and stick to them.

-At intervals the plates or vibrated and the dust falls down to a collector.

Static electricity is used in paint spraying:

-The gun is charged.

-All the pain particles become charged with the same charge.

-Like charges repel, giving it an even spray.

-The object to be painted is given the opposite charge to the paint

-Opposite charges attract so the paint sticks to it

-The object gets an even coat.

Defibrillation is the procedure used to restore a regular hearts read them by delivering an electric shock through the chest wall to the heart: 

-Two paddles are placed on the chest to ensure good electrical contact

-Electric charges passed through the patient to make the heart contract

-Great care has to be taken to ensure that the operator does not receive electric shock Variable resistor changes the resistance. Longer lengths of wire have more resistance as well as thinner wires.

Voltage is measured in volts using a volt meter connected in parallel:

For a fixed resistor as the voltage across it increases the current increases. For a fixed power supply as the resistance increases the current decreases. Variable resistor changes the resistance. Longer lengths of wire have more resistance as well as thinner wires. Voltage is measured in volts using a volt meter connected in parallel: For a fixed resistor as the voltage across it increases the current increases. For a fixed power supply as the resistance increases the current decreases.

The chance of getting an electric shock can be reduced by: 

-Correct earthing,

-Standing on insulating mat,

-wearing shoes with insulating soles.

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