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igcse physics notesprinted 101 · PDF 101
124 pagesrevision 46936
printed 101 · PDF 101
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101
A thermistor is a resistor whose resistance decreases as the
temperature increases.
A light dependent resistor is a resistor whose resistance decreases as light
intensity increases.
A relay is an electromagnetically operated switch. When a small current
passes through the
electromagnet, it switches on and attracts an iron arm. This arm rotates
about a pivot and pushes the contacts in another circuit together. They are
used to switch on a circuit with a high current using a circuit with a small
current
A diode allows current to flow in one direction only, because it has a very
high
resistance in the other direction. They can be used as a rectifier (i.e.
convert AC into DC).
Dangers of electricity:
Hazards:
● Damaged insulation – contact with the wire due to gaps in the insulation
can cause an
electric shock or pose a fire hazard by creating a short circuit.
● Overheating of cables – high currents passing through thin wire
conductors cause the wires
to heat up to very high temperatures which could melt the insulation and
cause a fire.
● Damp conditions – water can conduct a current so wet electrical
equipment can cause an
electric shock.
Fuses:
● A fuse is a thin piece of wire which overheats and melts if the current is
too high, protecting