Section 6 - Electricity Flashcards
(54 cards)
Define current
The rate of flow of charge
Which direction does conventional current flow?
positive to negative
Define a coulomb
The amount of charge that passes in 1 second when the current = 1A
Define potential difference
Work done per unit charge moved
What is the potential difference across components connected in parallel
The same
Define a volt
When you convert 1J of energy moving 1 coulomb of charge through the component
Define Ohm’s law
The current across an ohmic conductor is directly proportional to the potential difference when the physical conditions are kept constant
What do I/V graphs show?
How resistance varies
What does the I/V graph for an ohmic conductor look like
Straight line through the origin
I/V graph: What would a low resistance and high resistance look like on the graph?
Straight steep line for low resistance
Straight shallow line for high resistance
What is the I/V graph for a filament lamp?
A curve that starts steep but gets shallower, and passes through the origin
What is a filament lamp?
A coiled up length of metal wire
When does the resistance of a metal increase?
When the temperature increases
Why aren’t semi conductors as good as conducting as metals?
Far fewer charge carriers
What happens when you supply energy to a semi conductor?
Charge carriers are released
Why do semiconductors make good sensors?
Because when energy is supplied, more charge carriers can be released
What happens as temperature increases in a thermistor?
Resistance decreases
What does the resistance/temperature graph look like for a thermistor?
Top left to bottom right curve
What does the I/V graph look like for a thermistor?
bottom left upward curve to origin, top right downward curve from origin
What happens as the voltage increases in a thermistor?
Current increases
What happens to a thermistor as current increases?
It heats up, and resistance decreases -> graph curves upwards as more current can flow
Why does heating up a thermistor reduce resistance?
Gives electrons enough energy to escape from atoms -> more charge carriers
What do diodes do?
Only let current flow in one direction
What is forward bias on a diode?
The direction in which the current is allowed to flow
