Electricity Flashcards
in a circuit which way does conventional current flow
Positive to negative
in a circuit which way do electrons flow
negative to positive
what is current
the rate of flow of charged particles around a circuit or how many coulombs are flowing per second
what is 1 coulomb equivalent to
6x10^18 electrons
how does current work in series
because there’s no junctions all coulombs flow through all components , therefore current is the same throughout the circuit
what is voltage
amount of work done per coulomb by a component
how does voltage work in series
a voltmeter will measure how much energy a coulomb will have before and after a component which is why it needs to be connected in series
what is resistance
a component will have 1 ohm of resistance if 1V is required for 1A to pass through it
what is kirchhoffs second law
in a series circuit the sum of the voltages across each component must equal the voltage across the power supply
what is EMF also know as
electro motive force
the voltage across the power supply
what should resistance be in an ideal circuit
wires should have no resistance
ammeters in series and have no resistance to not impede electron flow
voltmeters in parallel and have infinite resistance to stop current flowing through
what makes a circuit parallel
it has multiple routes that a coulomb could go. these are called branches
how does voltage work in parallel
when a coulomb reaches a junction it can split it goes one way or another. so the voltage in each branch will be the same
how does current work in parallel
because voltage is the same in each branch the current will split in an even ratio between branches. however the greater ration will go down the path with least resistance
what is kirchhoffs 1st law
the current going into a junction must equal the current leaving the current AKA no current is lost in the circuit
what are tips for tricky circuit solving questions
write all value on the diagram
OHMS LAW
keep it simple
add series resistors first
what is an ohmic conductor and give an example
a component that follows ohms law
voltage is directly proportional to current (resistance is constant)
eg. fixed resistor
what are important features of an I against V graph
gradient is 1/R
steep line=low resistance
shallow line=high resistance
how do you check that a component is an ohmic conductor
you should reverse the direction of the current through it (switch the connection leads on power supply)
if the line remains straight (gradient) then its an ohmic conductor
what is a variable resistor
a long coil of wire where current flows through one end and out through a moveable slider. this is needed to check for an ohmic conductor.
a longer wire= greater resistance
what is a non-ohmic conductor and give examples
a component that does follow ohms law- there resistance isn’t constant.
eg. filament bulb, thermistor, diode, LDR
what is a filament bulb and draw an IV graph for it
a very long piece of wire is coiled inside a bulb. current flows through making it so hot it glows.
(check century for graph)
why does a filament bulb IV graph look like that
at the beginning the bulb is cold so there’s low resistance and electrons can flow through easily. when current is increased so is electron flow.
more electrons bump into the atoms in the wire passing them energy and vibrating harder heating up the wire. this means resistance is increasing
why might a filament bulb break
resistance starts off very low and heats up very quickly. the quick temperature change can cause the bulb to break
