Mains Electricity

Mains Electricity

Mains electricity (230 volts in the UK) is dangerous and can kill is not used safely.Electrical appliances can be connected to the mains using: a cable (containing an inner core of copper, and an outer layer of plastic), a plug containing a plastic case, brass pins, fuse, earth pin and a cable grip). Mains electricity is an a.c. supply.A fault in an appliance can cause the current to be too great and can lead to the wire overheating and possibly causing a fire. A fuse is designed to melt is the current through a circuit is too high, thereby breaking the circuit. The fuse should be just higher than the normal working current. A circuit breaker can be reset rather than replaced.Earth wire- If an appliance has a metal case it needs to be earthed. A fault could cause the live wire to touch the metal case. If the appliance is earthed, a large current flows down the earth wire and melts the fuse. If the appliance was not earthed there would be a risk of electrocution.

Fuses and Plugs

When a current flows in a wire, the ire can get hot. The wire can get hot enough to melt . Light bulbs have a piece of thin wire inside them which glows when electricity passes through it. A fuse is a piece of wire that is designed to melt if the current gets too high. This can prevent fires being caused if the wires get too hot.

Static Electricity

 Static electricity occurs when there is build up of electrical charge on the surface of a material. It is called static electricity because the charges don't move. The atom is made of 3 sorts of particles: The electron, the proton and the neutron. The protons and neutrons sit together in a lump in the middle called the nucleus. The electrons orbit around the nucleus a bit like the planets the sun. The electron is negatively charged. The proton is positively charged and the neutron has no charge, it is neutral. Most things have the same number of electrons and protons in them- they don't have any overall charge. If something has too many or too few electrons, it has a charge-too many electrons+ negative charge. Too few electrons= positive charge. Opposites attract, likes repel. Static electricity is caused when certain materials are rubbed against each other. Friction causes electrons to be rubbed off one material an onto another. The material that has got extra electrons is now negatively charged. Th material which has lost electrons is positively charged.

Static electricity (continued)

Static electricity is this imbalance of positive and negative changes that causes balloons to stick to walls; your hair to to stand on ends when brushing hair on a dry day and the electric shock you sometimes get from your car.Lightning is actually just static electricity on a much larger scale. The rubbing is caused by air and water vapour moving around in the cloud. 

Current

Electron are tiny negatively charged particles that orbit the nucleus of atoms. In a metal these electrons can leave the metal atoms and flow in the conductor.The flow of charge transfers energy from the battery to components in the circuit like bulbs. Energy can also be transferred in the form of heat in to the wires if the current is high.A battery makes electrons in the wire start moving in one direction because they are attracted to its positive terminal.Bigger batteries (more voltage) make more electrons start to move, smaller batteries (less voltage) can only make a few electrons start to move.The amount of resistance also affects the current. Poor current is completely determined by the resistance and size of the battery. Low resistance means more charges can flow. High resistance means less charges can flow.

Voltage

Voltage is the amount of energy the battery gives to the current. Voltage is a measure of the difference in electrical energy between two parts of a circuit. The bigger the difference in energy the bigger the voltage. The voltage is measured in volts. The symbol for volts is V. For example 230V is a bigger voltage than 12V.Voltmeters are connected in parallel.

Electrical Resistance

Resistance is opposition to the flow of charge in a circuit, this happens when charges collide with atoms in the component or resistor.A fixed resistor is used to make the current smaller in a circuit, there are lots of sizes.A variable resistor is used to vary resistance in a circuit. (Volume controls; dimmer lights)

Parallel and series circuits

Parallel circuits have two or more branches; each branch is connected to the same battery; each branch is independent to the others; a branch can have one or more component in it.The voltage is the sam across the cell and each branch of a parallel circuit. The circuit splits across each branch but the amount of current depends on the component in that branch.In a series circuit the voltage splits across each component depending on the resistance of that component. The current is the same at all points of a series circuit.