Topic 2 - Electricity Flashcards
Explain how to know the current, pd and resistance of a series circuit
Current - Same throughout
Pd - Shared
Resistance - Add the resistance of all components
Explain how to know the current, pd and resistance of a parallel circuit
Current - Shared
Pd - Same throughout
Resistance - Can not calculate (will be lower than smallest resistance)
Explain ac and dc - give examples for both
Ac - alternating current - constantly going positive to negative - e.g. Mains supply
Dc - direct current - always staying in one direction - e.g. Batteries
Explain and give the colours of the 3 wires in cables/plugs
Live wire - Brown - Provides AC at 230V from the mains
Earth wire - Yellow and green - Used to stop the metal from becoming live when something goes wrong. 0V
Neutral wire - Blue - Completes circuit and takes current out - 0V
What is the national grid?
Giant system of cable and transformers that connects power stations to consumers.
Why does the national grid use high Pd and low current?
High current would lose energy through the wires and into the surroundings. This means that pd is boosted really high whilst current is kept low.
What is used to increase and lower the pd?
Step up and step down transformers
Explain how static is caused
Two insulating materials are rubbed together so negatively charged electrons get dumped from one object to another meaning the objects have equal positive and negative charges
What is an electric field? How is it created
An electric field is created by any electrically charged object - the closer you get, the stronger the field is.
How can sparks be explained in terms of electric fields.
Sparks are caused when there is high pd between a charged and earthed object, This causes a strong electric meaning electrons in the air are removed (ionisation). This turns the air into a conductor meaning current flow through it
What are the three equations for calculating power
Energy transferred = Power x Time.
Power = Current^2 x Resistance
Power = Pd x Current
What is the power rating of an object?
The maximum safe power it can operate at.
What is an LDR and thermistor?
LDR - light dependent resistor - as light increases, resistance lowers
themistor - temperature dependent - as temperature increases, resistance lowers
Explain the I-V graph of an ohmic conductor, filament lamp and diode
Ohmic - Straight diagonal line passing through origin
lamp - curved near top and bottom,
diode - starts above 0 as current only flows one way.
