You charge an insulating material by rubbing it with a cloth
the two types of charge are positive and negative
the transfer of electrons cause electrostatic effects
some charged materials attract others such as small pieces of paper to a comb
like charges repel and unlike charges attract
you can get a shock from
synthetic clothing
earthing yourself after becoming charged
static electricity in terms of movement of electrons
negative = gain
positive = loss
the chance of shock can be reduced by
earthing
insulating mats
insulated footwear
P4b
defibrillator
A defibrillator is a machine that can be used by paramedics to stabilise
an irregular heartbeat. They work by discharging electric charge.
Two paddles with insulated handles are charged from a high voltage supply. They are put in good electrical
contact with the patient's chest. It is important that only the patient gets a shock:
The defibrillator passes charge through the patient to make the heart contract.
dust precipitators
Many power stations burn fossil fuels such as coal and oil. Smoke is produced when these fuels burn.
Smoke comprises tiny solid particles, such as unreacted carbon, which can damage buildings and cause
breathing difficulties. To avoid this, the smoke is removed from waste gases before they pass out of the
chimneys. The electrostatic precipitator is the device used in chimneys for this job.
Smoke particles pick up a charge as they pass the charged metal grid. These smoke particles are attracted
to oppositely charged collecting plates.
paint spraying
The paint spray goes past a high voltage positive needle as it leaves the spray gun and the tiny droplets of
paint pick up a positive charge. They do this by losing negative electrons. It is only the electrons that can
move.
This improves efficiency in two ways.
1. The paint droplets spread out more as they leave the gun. This happens because they all
get the same positive charge and so they all repel each other. This is better than coming
straight out of the gun as the paint will cover a wider area more evenly as shown in the
picture below. The same thing happens with insecticide crop spraying.
2. The paint droplets are attracted to the negative metal car body, and so less paint will be wasted by landing
on the floor or the walls of the paint shop.
P4c
resistors / variable resistors can change the current in a circuit
equation Resistance = voltage / current
live, neutral and earth wires
live is brown
Earth is Yellow and green
Neutral is blue
double insulated appliances do not need earthing
plastic casing cannot become live
how a wire fuse protects an appliance by splitting the circuit if the current becomes too high
fuses and circuit breakers prevent house fires and other simillar risks from occurring