E&E Flashcards
What happens to voltage in a series circuit?
It’s is shared between the components
Formula for Vs
Vs=V1+V2
What happens to current in a series circuit ?
It is the same at every point
The resistance of an electrical component is defined as:
The voltage across it divided by the current through it
Three parts of electronic system
INPUT-PROCESS-OUTPUT
What does the input device do ?
The input device changes one from of energy to electrical energy.
Example of input devices
Two examples of INPUT devices are solar cells (light) and thermistors (temperature change).
What does the process device do ?
The process device then does something to the electrical signal e.g. an amplifier makes it larger.
What does the output device do ?
Next, the output device converts the processed electrical signal into another form of energy e.g. an LED produces light.
How does an and gate activate an output ?
For an AND gate to activate an output, both inputs musts be on.
How does an or gate activate and output ?
For an OR gate to switch on the output device, either input can be on.
For example, to switch on a car interior lamp if a passenger OR the driver opens a door then you would have switches (inputs) on each door and an OR Gate to turn on the lamp.
Electricity generation
Electricity is generated in a variety of ways. There are two main categories for generating electricity: non-renewable and renewable energy resources.
Non renewable energy resources
Most non-renewable energy resources use fossil fuels (coal, oil and natural gas) to generate electricity. In fossil fuel generators, the chemical energy of the fuel is burned to release heat energy.
What are magnets attracted to ?
- Magnets are attracted to certain metals, e.g. iron and steel.
- The ends of a magnet are called the North and South poles.
What is used to show the magnetic field around a magnet ?
- Iron filings can be used to show the magnetic field around a magnet.
- Magnetic field lines have arrows on which point from North towards South.
What produces a magnetic field
• A wire with a current flowing in it produces a magnetic field.
How is an electromagnet made ?
• An electromagnet can be made by winding insulated wire around an iron core and passing current through the wire.
What is a transformer?
• A transformer consists of two coils wound around the same iron core.
What do transformers do?
• Transformers use a.c. (alternating current) in the primary coil to create a constantly changing magnetic field. This changing magnetic field causes a voltage across the secondary coil. The size of the voltage depends on the number of turns in the coils. If the secondary coil has more turns than the primary coil, it will have a bigger voltage.
What are transformers used for ?
- Transformers are used to ‘step up’ and ‘step down’ voltage in electricity distribution systems to reduce energy losses in transmission lines.
- Transformers are also used in adapter plugs for electronic equipment, e.g. phone chargers, laptops.
Non-renewable sources – will eventually run out
Fossil fuels (coal, oil and gas) Nuclear power.
Renewable sources – will not run out
Hydroelectric power Wind power Solar power Geothermal power Wave power Tidal power
What do generators do ?
Most methods of producing electrical energy use a generator. This transfers kinetic energy (movement) into electrical energy using electromagnetism.
To generate electrical energy, a coil of wire must be near a changing magnetic field. This can be done by;
- Moving a coil near a magnet or
2. Moving a magnet near a coil
What does a power rating of an appliance tell us ?
The power rating of an appliance tells us how much electrical energy it changes into other forms every second.
Cost of using electrical appliances
The cost of using an electrical appliance is affected by two factors:
• The power rating of the appliance.
• The period of time that it is switched on for.
Efficiency of electrical appliances
No appliance is ever 100% efficient, because some electrical energy is always transferred into unwanted forms of energy
What does a flex do ?
• The fuse protects the flex from overheating. It melts and breaks the circuit if the current gets too high.
