4. (a) Electricity Flashcards
What is electric field
A region in which an electric charge experience a force
What is charge measure in
Coulomb
What is the line of force
Path a free positive charge would take if released in the field
What is voltage across A and B
Total energy required to move a coulombs of charge from a to b
What is current
The flow of electric charge within a circuit
Measured in A
How to calculate current
Q = I x t
How to calculate resistance
Voltage / current
How to increase resistance
Increase the length of the wire
Reduce the cross section
Increase the temperature
Describe the thermistor
Resistance increase, temperature decrease
Resistance decease, temperature increase
Describe the LDR
Resistance increase, light darker
Resistance decrease, light brighter
Describe the current in series
Current is the same everywhere
I1 = I2 = I3
Describe current in parallel
I total = I1 + I2
Describe the voltage in series
V total = v1 + v2
Describe the voltage in parallel
I Voltage is the same everywhere
V1 = v2 = v3
Describe the resistance in series
R total = r1 + r2
Describe the resistance in parallel
1/ r total = 1/r1 + 1/r2
Explain the term ‘digital signals’
A series of pulses consisting of just two states
+ on (1)
+ off (0)
There is no values in between
Explain the term ‘analogue signals’
Signals that can vary in frequency, amplitude or both
What are logic gates
Circuits containing transistors and other components
Digital circuit designed to make a decision, it gives an output voltage determined by the input voltage
Describe the danger of damaged insulation in a wire
The layer of insulation around a wire may wear away
A plug or socket may become chipped or broken, exposing a bare wire
Contact with the wire due to gap in insulation causes electric shock
Describe the dangers of overheating cable
Too much current through a wire of a cable -> overheating -> insulation of the wires soften or melt -> exposing wire in the cable
A coiled cable in use could overheat bc the heat has less area to escape -> might cause fire
Describe the dangers of damp conditions in electricity
Water can conduct a current, providing a conducting path to the outer surface
Anyone touching the device could then suffer an electric shock
Describe the use of fuse
Contains a thin wire that heats up and melts if too much current passes through it -> break the circuit
The rating of a fuse is the maximum current that can pass through it without melting the fuse wire
Describe the use of circuit breaker
It is an electromagnetically-operated switch in series with an electromagnet
The switch is held closed by a spring
When the current exceeds a certain value -> the electromagnet pulls the switch open -> current is cut off
They work faster than fuse and can be reset quicker
