Resistance Flashcards
formula for calculating resistance
R = V / I (resistance = potential difference / current)
in the formula triangle involving V R and I, which one is at the top
V
what does an ammeter measure
the current in amps flowing through the test wire
where must the ammeter always be placed
in series
what does a voltmeter measure
the potential difference across the test wire, in volts
where must the voltmeter always be placed
in parallel around what you are investigating
what is the current flowing through an ohmic conductor at a constant temperature
it is directly proportional to the potential difference across it
what is an ohmic conductor
a wire or resistor
what is specific to ohmic conductors in circuits
their resistance doesnt change with the current, so R is constant
what happens when an electrical charge flows through a filament lamp
it transfers some energy to the thermal energy store of the filament, which is designed to heat up
what is the effect of a filament lamp increasing in temperature
resistance increases with temperature, so as the current increases, the filament lamp heats up more and the resistance increases
what does the resistance depend on for diodes
the direction of the current. they will allow current flow in one direction, but have a high resistance the other way
what is an I-V characteristic graph
a graph which shows how current flowing through a component changes as the potential difference across it is increased
how do linear components, like a fixed resistor, look like on an IV graph
a straight line
how do non linear components, like a filament lamp, look like on an IV graph
a curved line
