P4 - circuit electricity Flashcards
Describe a single cell
Provides the circuit with a source of potential difference
Describe a battery of cells
A battery is two or more cells
Describe a switch
Turn the circuit on (closed),or off (open)
Describe a resistor
A resistor limits the flow of current
Describe a fixed resistor
A fixed resistor has a resistance it cannot change
Describe a thermistor
The resistance of a thermistor depends on the temperature ,as it’s temperature increases then the resistance increases.
What does LDR stand for
Light dependent resistor
Describe a LdR
The resistance of LDR depends on the light intensity
What is a electric current
It’s the flow of charge
What charge do electrons carry
A negative charge
What determines the size of the current
Determined by the flow of charge (the flow of charge per second)
Why are metals good conductors?
Metals contain lots of free electrons that can move freely between the positively charged metal ions
What is the equation to calculate charge?
q= It
What is the unit for charge?
Coulombs , C
What is the unit for current?
Amps,A
What is the equation for potential difference?
V= E/q or E= Vq
What’s it called when electrons that pass through a wire have to push their way through lots of vibrating ions in the metal?
Resistance
What’s the equation for resistance?
Resistance= potential difference/ current
V=IR
What is resistance measured in?
Ohms
The longer the wire the ………… resistance
Higher
What are the series circuit rules?
Current - stays the same
Voltage - shared between the components
Resistance- add together
R total = R+ R2+R3…
What are the parallel circuit rules?
Current- split along branch
Voltage - stays the same
Resistance- as more resistors are added,total resistance increases.
Describe a fixed resistor graph
- constant gradient
-directly proportional
-straight line
-through origin 0,0
