# 2 Electricity - iGCSE Physics Edexcel

2.1 use the following units: ampere (A), coulomb (C), joule (J), ohm (Ω), second (s), volt (V) and watt (W)
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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 and circuit breakers:
● A fuse is a thin piece of wire which overheats and melts if the current is too high, protecting the circuit. They have a current rating which should be slightly higher than the current used by the device in the circuit. The most common are 3A, 5A and 13A.

● Circuit breakers consist of an automatic electromagnet switch which breaks the circuit if the current rises over a certain value. This is better than a fuse as it can be reset and used again, and they operate faster. Earthing metal cases:

● Earth wires create a safe route for current to flow through in the case of a short circuit, preventing electric shocks.

● Earth wires have a very low resistance so a strong current surges through them which breaks the fuse and disconnects the appliance.

Double insulation:
● Appliances with double insulation have either plastic casings completely covering their electrical components, or have been designed so that the earth wire cannot touch the metal casing, preventing them from giving an electric shock.
Relationship between voltage and current can be different for different types of components and is shown by an IV graph
Current=Y
Voltage=X

Resistor
-Linear line
-Through the whole graph

Filament lamp
-Resistance increases with temperature
-Slight plateaus on the ending of both sides of curve

Diode
-Only allows current to pass in one direction
-Line at Y=0 until certain point
-Around halfway through, Y begins to increase in linear fashion
Investigation
Set up a circuit with:
-Ammeter in series
-Voltmeter in parallel to component

Starting with a low voltage, slowly increase the voltage of the power supply over a range of settings (e.g. from 1V to 12V in 1 V intervals).
Record the readings on the ammeter and voltmeter as you do so.
Repeat the experiment 3 times and take an average.