P2 Electricity Flashcards
What is electricity?
The flow of charge of electrons.
How does current flow?
Positive to negative.
What is the unit for charge?
Coulombs (C).
What is potential difference?
The measure of how much energy is transferred to/by each Coulomb of charge.
What is the unit for PD?
Volt (V).
How are voltmeters placed in a circuit?
In parallel.
How are ammeters placed in a circuit?
In series.
What is current?
The rate of flow of charge.
What is the units for current?
Amps/Amperes (A).
What is resistance?
The measure of how much a component/object resists the flow of current.
What are the units of resistance?
Ohms.
What is the relationship between Current and PD with fixed resistors?
Directly proportional.
What is the relationship between current and pd with a filament lamp?
larger current = increased resistance.
What is the relationship between current and pd with a diode?
current flows in one direction. Low resistance in forward direction, high resistance in reverse direction.
Characteristics for series circuits.
Total PD is shared between all components
current is the same for all components
total resistance = sum of resistances.
Characteristics for parallel circuits.
PD for each branch = PD of cell/battery
current is split between branches
adding more resistors in parallel reduces total resistance.
What is a thermistor?
A thermistor can detect changes in temperature. If the temp increases, the resistance of the thermistor decreases.
What is a light dependent resistor?
An LDR can detect changes in light. If light intensity increases, resistance decreases.
What is DC?
Direct current. Current that only flows in one direction.
What is AC?
Alternating current. Current that flows in both directions.
What is the UK mains voltage?
230V
Which wire is the brown wire?
The live wire.
Which wire is the blue wire?
The neutral wire.
What is the yellow and green wire?
The earth wire - safety feature.
What is a fuse?
A thin metal wire in a tube that is designed to melt or ‘blow’ if there is a fault that causes a high current. They are usually 3A, 5A or 13A.
What is the national grid?
A mixture of power stations, cables and more which transmit power across a country.
What is a step-up transformer?
Increases the voltage to around 132kV, which decreases the current, reducing the power lost due to heating the cables.
What is a step-down transformer?
Reduces the voltage down to a safer and usable 230V for homes and businesses.
