electricity - resistance Flashcards
What is resistance?
A measure of how difficult it is to pass an electric current through a component.
What is resistance cause by?
The electrons that flow colliding with atoms of the component.
What does the resistance of a component depend on?
The potential difference across it and the current flowing through it.
What is resistance measured in?
ohms
What is the equation to find resistance?
V = IR
potential difference = current x resistance
When p.d increases what does the current do?
It also increases
What does the total resistance equal?
R1 + R2 + …
How does the difference in the thickness of the wire effect the resistance?
The thicker the wire, the lower the resistance
What is resistance in a wire affected by?
The length of the wire
The thickness of the wire
The temperature of the wire
The material of the wire
What is the resistance of a filament lamp?
resistance increases as it gets brighter and hotter.
What resistance graph is this?
https://i.stack.imgur.com/5dg9x.gif
a filament lamp
Does a filament lamp obey ohms law?
no
What is ohms law?
A law stating that electrical current is proportional to p.d and inversely proportional to resistance.
What is the resistance like in an ohms resistor?
It is constant
Does an ohms resistor obey ohms law?
yes
What resistance graph is this?
https://o.quizlet.com/ygEG3rgWKsMlpXd5xo-1OA.png
ohms resistor
What is the resistance like in a diode?
If it is forward biased it has zero resistance
When it is reverse biased it has infinite resistance
What resistance graph is this?
https://www.ossila.com/files/1/0823/0287/files/diode-iv-curve.png?1999614258181120511
a diode
What is the resistance like in a LDR (light dependent resistor)?
changes resistance with varying light intensity.
What resistance graph is this?
https://images.twinkl.co.uk/tr/image/upload/t_illustration/illustation/Light-Intensity-LDR-and-Resistance-Graph-Answer—Edexcel-Science-Secondary.png
a LDR (light dependent resistor)
What is the resistance like in a thermistor?
It changes it resistance with temperature
What resistance graph is this?
https://www.google.com/url?sa=i&url=https%3A%2F%2Fwww.ametherm.com%2Fthermistor%2Fntc-thermistor-beta&psig=AOvVaw2kkFh2ou7zJg6N-6v_K-p2&ust=1636701545947000&source=images&cd=vfe&ved=0CAsQjRxqFwoTCOiFzcfij_QCFQAAAAAdAAAAABAD
a thermistor
What does a sensing circuit do?
it turns on or increases the current to components depending on the conditions they are in.
What does a wire do?
It is an electrical conductor that is ohmic
What does a resistor do?
It limits the flow of current
What does a filament lamp do?
It has a thin wire that heats up when the current flows and emits light
What does a diode do?
It only allows current to flow in one direction
What does a LED do?
It only allows current to flow in one direction and emits light.
What does a LDR do?
As light intensity increases, resistance decreases
What does a thermistor do?
As temperature increases, resistance decreases
what is the equation to find power
Power = current squared x resistance
