P4 - Electrical Circuits Flashcards
What is a battery?
2 or more cells joined together.
Ohm’s law?
Current through a resistor at a constant temp is directly proportional to the potential difference across the resistor.
Reversing the potential difference through a resistor….
Reversed the current through it.
Why do insulating materials become charged?
because electrons are transferred
D. Current
Flow of charge
What is electric charge measured in?
coulombs
D. Diode?
a non-ohmic conductor that has a much higher resistance in one direction then the other so allows current only one way.
1 Amp is….
I coulomb/second
Why are voltmeters connected in parallel?
So that it measures the voltage across something/a component
Current is directly proportional to….
resistance
D. Thermistor
A temperature-dependant resistor, temp increase = resistance decrease
E. Total resistance for a series circuit
T.R = R1+R2+R3 etc
E. Total resistance for a parallel circuit?
1/t.r = 1/R1 + 1/R2
In a series circuit?…. (current and P.D)
Current is the same everywhere, P.D is shared equally through the components
In a parallel circuit….
Current is split and P.D is the same everywhere?
Putting more resistors in parallel….
Decreases total resistance of circuit because total current through them is increased and P.D is unchanged
Why does a filament lamp’s resistance change as P.D changes?
Because as P.D increases the temp increases, so the metal ions have more k.energy and vibrate more vigorously and so it is harder for the electrons to pass through them, which means that the resistance is increased.
