National 4 EE Flashcards
What are our main sources of energy?
Fossil fuels: coal, oil and gas.
What does FINITE mean when describing fossil fuels?
It means that the fossil fuels will eventually run out and take a long time to form.
What are the main sources of renewable energy?
Solar Wind Waves Tidal Geothermal Hydroelectric Biomass
What are the main sources of non-renewable energy?
Coal Oil Gas Peat Nuclear
What is an advantage of renewable energy sources?
They will never run out because they are renewable.
What is an advantage of non-renewable energy sources?
Produce a lot of energy.
What is a transformer?
A device that can change the size of an ac voltage. It can either increase or decrease the size of a voltage.
Describe the structure of a transformer.
Consists of two seperate coils of wire wound in the same iron core.
What equation describes the relationship between the voltage and the number of turns for the primary and secondary coils of the transformer?
Secondary Voltage/ Primary Voltage= Secondary Number of Turns/ Primary Number of Turns
or Vs/ Vp= Ns/ Np
What equation should be used to calculate efficiency?
Efficiency= Output/ Input (Power or Energy)
What happens to the voltage when a coil wire is moved within a magnetic field?
There is induced voltage when the wire moves up and down between the poles.
What factors affect the size of an induced voltage when a wire is moved within a magnetic field?
Moving the wire faster between the poles of the magnet
Using a stronger magnet
Use more conductor eg. make a few turns of the conductor.
How are electrons arranged in a conductor?
The electrons are free to move throughout the structure.
How are electrons arranged in insulators?
The electrons are tightly bound and cannot move.
What is the electric current in an electrical circuit?
The flow of electrons around a circuit. (the greater the flow, the greater the current)
Describe a series circuit.
When components are connected in line, it is said to be connected in series.
What is the unit of current?
Amperes (A)
What is the current at different points in a series circuit?
The same as the current from the battery.
A1= A2= A3
Describe a parallel circuit.
When components are connected so that there is more than one path for the current, it is said to be connected in parallel.
What is current like in a parallel circuit?
The sum of currents through each component in a parallel circuit, adds up to the current which flows from the supply
A= A1+ A2
What is the voltage in an electrical circuit?
The electrical energy supplied by the battery to make the electrons move around the circuit.
What is the unit of voltage?
Volts (V)
What is voltage like in a series circuit?
The sum of voltages across each component in a series circuit adds up to the supply voltage
V= V1+ V2
What is the voltage at different points in a parallel circuit?
The same as the supply voltage.
V1= V2= V3
What is resistance in an electrical current?
The opposition to the flow of current in a circuit
What is the unit of electrical resistance?
Ohms (Ω)
What are some factors that affect resistance?
Type of material- the better the conductor, the lower the resistance
Length of material- the longer, the higher the resistance
Thickness of material- the thicker, the lower the resistance
Temperature of material- (usually) the higher, the higher the resistance
What happens to the current in a circuit when resistance in the circuit changes?
If resistance increases, the current decreases.
What is the equation to calculate the resistance? (Ohm’s Law)
Resistance= voltage/ current R= V/I
What are some practical applications of a variable resistance?
Light dimmer controls
Volume and brightness controls
Speed controls on electric motors
What energy transformations take place in electrical appliances?
Electrical energy—-> other form of energy
What is the unit of energy?
Joules (J)
What is the power rating of an appliance measured as?
The number of joules of energy it transforms per second
What is the unit of electrical power?
Watts (W)
What is the equation involving energy, power and time?
Energy= power x time E= P x t
What are the three parts of an electronic system? (in order)
The input, the process, the output
What are examples of input devices?
Thermistor
LDR
Switch
What is the energy change in a microphone?
Sound energy—-> Electrical energy
What happens to the resistance of a thermistor with changes in temperature?
High temperature- Low resistance
Low temperature- High resistance
What happens to the resistance of an LDR with changes in light levels?
Bright- Low resistance
Dark- High resistance
What are appropriate input devices for given applications?
Microphone- loudspeaker
Thermistor- heating system
LDR- automatic lamp
Switch- lighting circuit
What is the energy change in an output device?
Electrical energy—–> another form of energy
What are some examples of output devices?
Loudspeaker Buzzer Lamp LED Electric motor
What are appropriate output devices for given applications?
Loudspeaker- radio
Buzzer- smoke alarm
LED- warning light
Motor- fan
How do you draw a NOT gate?
Triangle with a small circle and one line at each side.
How do you draw an AND gate?
Semi circle, two lines at the left side (input) and one at the right side (output).
How do you draw an OR gate?
Weird curved shape with two at the left and one on the right.
What does the truth table for a NOT gate look like?
Input Output
0 1
1 0
What does the truth table for an AND gate look like?
Input A B Output 0 0 0 0 1 0 1 0 0 1 1 1
What does the truth table for an OR gate look like?
Input A B Output 0 0 0 0 1 1 1 0 1 1 1 1
Describe solids in terms of the arrangement and movement of the particles.
Particles are arranged very close together and vibrate (move) in the one spot.
Describe liquids in terms of the arrangement and movement of the particles.
Particles are arranged close together and they swap places with their nearest neighbouring particles.
Describe gases in terms of the arrangement and movement of the particles.
Particles are arranged far apart and they move very fast/ randomly in all directions.
