Section 2 - Electricity Flashcards
What are the main hazards of electricity?
- Frayed Cables - live parts might be uncovered
- Long Cables - could be a trip hazard
- Damaged Plugs - live parts might be uncovered
- Water Around Sockets - water is a good conductor
- Pushing Metal Objects Into Sockets - metals conduct electricity
What is insulation of a plug?
Insulation is covering a live wire with a material that won’t conduct electricity
What is double insulation of a plug?
Double insulation is a precaution that makes sure the live wire does not touch the casing of the plug by putting extra insulation around the wire. It can also mean that the casing is plastic so it won’t conduct electricity
What is an earth wire?
An earth wire is touching the case so if a current is in the case, it will be directed through the earth wire, which will then take the current to the earth.
What are fuses?
Fuses are section of wires that melt if the current is too high. They come with different maximum currents
What are circuit breakers?
Circuit breakers have an electromagnet that is activated if the current goes above a certain limit. The electromagnet pulls an iron switch towards it, which opens the switch and breaks the circuit.
What happens if a current travels through a resistor, and what can it be used for?
When there is an electric current in a resistor, there is an energy transfer which heats the resistor.
It can be helpful in domestic appliances such as toasters or old-style light bulbs
What is the equation for POWER?
Power = Current x Voltage
How can we work out which fuse is appropriate for an appliance?
You want a fuse which melts at a certain current, which is just above the normal operating current
What is the equation for ENERGY TRANSFERRED?
Energy Transferred = Current x Voltage x Time
What is the difference between a.c. (mains electricity) and d.c. (a cell or battery(?
The current is constantly changing direction in a.c.
The current keeps flowing in the same direction in d.c.
Why are series circuits used in some domestic appliances?
In series circuits, if one component breaks or is removed, no current will be able to flow. Therefore, the circuit cannot be used.
This is not very useful often, but there are some cases. For example, fairy lights
Why are parallel circuits used in some domestic appliances?
In parallel circuits, each component is separately connected, so if you remove one of them, it will hardly affect the others.
This is very useful, so it is used in domestic lighting
What does the current depend on in a series circuit?
The current is the same everywhere in the circuit.
We can change the size of the current by increasing the voltage or by decreasing the resistance
What effect do wires, resistors, metal filament lamps and diodes have on the current of a circuit, and how can we show this?
They all create resistance in a circuit, so the current will decrease.
This can be shown by using an ammeter to measure the changes in current when one of these components are added or removed
What is an LDR and what does it do?
An LDR is a light dependent resistor. The brighter it is, the less resistance it creates
What is a thermistor and what does it do?
Thermistors are temperature dependent resistors. In hot conditions, there will be less resistance.
How can lamps and LEDs be used to indicate the presence of a current?
LEDs and Lamps require a current to light up. If the LED or Lamp is in a circuit and does not light up, then there must be no current
What is the equation for VOLTAGE?
Voltage = Current x Resistance
What is current?
Current is the rate of flow of charge
What is the equation for CHARGE?
Charge = Current x Time
What is an electric current within a solid metallic conductor?
It is the flow of negatively charged electrons
What is voltage? *
Voltage is the energy transferred per unit charge passed
What is the equation for a VOLT? *
Volt = Joule / Coulomb
What are good electrical conductors and give an example?
Electrical conductors require materials to allow the free movement of charged particles. Therefore, metals are good conductors
What are bad electrical conductors and give an example?
Bad electrical conductors do not allow charged particles to move freely. therefore, plastics (a polymer) is a bad electrical conductor
Describe an experiment to show how insulating materials can be charged by friction *
Rub a polythene and acetate rod with a cloth duster. The polythene rod will become negatively charged and the acetate rod will become positively charged
Why do the objects in the experiment where you rub two insulating objects together gain an electrostatic charge? *
Electrons are transferred from one to the other. As the charges are not flowing, it is an electrostatic charge.
What happens when two like charges come together? *
There are forces of repulsion
What happens when two unlike charges come together? *
There are forces of attraction
Describe electrostatic phenomena *
When electrons move from one material to another, the material with a negative charge will then look for some way to earth its charge. An example of this are clouds use lightening and a car uses your hand and body
What are the potential dangers of electrostatic charges? *
When a large electrostatic charge builds up, it can create a spark. When fuelling vehicles, the fuel rubbing along the pipe can cause an electrostatic charge, which if it sparks, could ignite the fuel and cause a fire. So, the charge is brought to earth by a wire attached to the plain or tanker
Explain some uses of electrostatic charge *
They are used within inkjet printers and photocopiers.
These machines give the ink a charge and the parts of the paper where it is wanted the opposite charge. Therefore, the ink is automatically attracted to the right parts of the paper.
