Revision Video for the Electricity Unit

A really helpful revision video for the electricity unit. 

2.8 Series vs Parallel circuits

Series circuits are only suitable for low voltage devices like fairy lights. These are are bit easier to produce as the wiring is easier. However, the voltage is shared amongst the components even though the current is the same. Also components cannot be switched off individually.

Parallel circuits are more practical. Components can be switched off individually and voltage remains the same for each component even though the current is shared. These are suitable for high voltage devices like lamps and air conditioners.

2.7 DC vs AC current

DC comes from things like cells and batteries

AC comes from generators

In alternating current the electrons flow in both the directions which is changed at a frequency of 50 hz in the UK. Mains electricity runs on AC current.

In direct current the electrons only flow in one direction from negative to positive terminal.

An inverter is needed to convert between these.

2.5 Relationship between power, current and voltage and application to fuses

Power = current x voltage

Power in Watts (W)

Current in Amps (A)

Voltage in volts (V)

Applying this to find fuse rating.

Lets a lamp runs on 60W, and 220 Volts.

You have to find the current  

Current = power/voltage

60/220 = 0.27

Fuses will usually come in 3A, 5A and 13A rating so the next higher will be used.

So for this lamp we will use the 3A fuse.

2.4 conversion of energy in resistors and applications

A resistor slows down the flow of electrons hence decreasing the current that can pass threw it. This kinetic energy is converted into heat energy which can be used in appliances like heaters, hairdryers and electric hobs.

2.3 Uses of some electricity safety features

• Insulation – using a non conductive material like plastic to cover electronic components
• Double insulation – appliances with plastic casing
• Earthing – connecting an extra wire to an appliances metal casing will take away the current and blow the fuse in case the live wire comes loose and touches the metal casing of the appliance. The fuse blows because, the earth wire draws a large amount of current hence overloading the fuse and safely shutting off the appliance.
• Fuses – fuses break the circuit and prevents an appliance from getting damaged in case too much current is coming from the socket
• Circuit breakers – these are like fuses that break a circuit when too much current is flowing thru. But they are more quick and they can be reseted. However, they are more expensive and less compact

2.2 Hazards of electricity

• Frayed wires – can cause electrocution
• Long wires – can heat up and cause a fire; because they have a lot of resistance
• Damaged plugs – some safety features like fuses may not work or the plug may cause electrocution
• Water around sockets – can conduct electricity and cause electrocution
• Pushing metal objects into sockets – can conduct electricity and cause electrocution
• Overloading sockets – can overheat and cause fire