resistors Flashcards
1
Q
what is directly proportional to current?
A
potential difference
2
Q
give examples of components where resistance changes depending on current
A
filament lamp
diode
3
Q
describe why resistance changes in a filament lamp
A
- when a charge flows through, it transfers some energy to the thermal energy store of the filament which is designed to heat up
- resistance increases with temperature so as the current increases the filament lamp heats up more, and resistance increases
4
Q
describe resistance in a diode
A
- current through a diode only flows in one direction
- diode has a very high resistance in the opposite direction
5
Q
why does resistance increase?
A
when there is a temperature increase
6
Q
what does resistance tell us?
A
the potential difference required to drive a current through a component
7
Q
describe current, pd and resistance in an ohmic conductor at constant temp?
A
- current is directly proportional to the potential difference across a resistor
- means resistance remains constant as potential difference changes
8
Q
thermistor resistance relationships
A
- resistance decreases as temp increases
9
Q
uses of thermistors
A
- temperature detectors e.g car engine temp sensors, electronic thermostats
10
Q
ldr resistance relationship
A
- resistance of an LDR decreases as light intensity increases
11
Q
ldr uses
A
- automatic night lights
- outdoor lighting
- burglar detectors
