electricity Flashcards
what is current
it’s the rate of flow of charge
what is an ohmic conductor
they are the conductors that obey ohms law
this is when current is directly proportional to pd
they’re only true if the conductors are under constant physical conditions like temp
what are semiconductors
explain with reference to charge carriers how an NTC thermistor connected in a circuit can
as the temp of the thermistor increases more charge carriers are released.
more charge carriers available allows more current to flow in the circuit
so the current in the circuit can be used to monitor the temp
what are three things that determine resistance
length — the longer the wire the more difficult it is to make a current flow
area — the wider the wire the more easier it will be for the electrons to pass along it
resistivity — which depends on the material. the structure may make it easier or difficult for charge to flow
it depends on environmental factors like temp and light intensity
what’s resisitivity of a material
it’s defined as the resistance of a 1m length with a 1m^2 cross sectional area
it is measured in ohm meters
what’s a superconductor
conductors that have no resistivity usually all conductors have resistivity unless they are cooled down enough which is REALLY expensive
They’re materials that resistance decreases to 0 at the critical temp
what are uses of superconductors wires
- power cables that transmit electricity without any loss of power
- really strong electromagnets that don’t need a constant power source
- electronic circuits that work really fast, because there’s no resistance to slow them down
how do you know a conductor is a superconductor with K
when it is below its critical temperature
What happens to the current, pd, and resistance in series circuit
Total pd is shared between all components
Current is the same for all components
Total resistance equals to sum of resistance
What happens to the current, pd, and resistance in parallel circuit
Pd for each branch are equal
Current is split between branches
Adding more resistors in parallel reduces the total resistance 1/R + 1/R =totalR
What’s kirchhoffs 2nd law
The sum of EMFs must equal the sum of pd drops in a closed circuit
what is current
it’s the rate of flow of charge
why does resistance change for a metal
the delocalised ions collided with ionic lattice which causes more vibrations so more temp
why is diode graph like that
the resistance go from really low to really high
what’s kirchhoffs first law
charge is conserved at any junction in a circuit
total current in = total current out
