More circuit calculations Flashcards
what to do for every circuit question
sketch circuit diagram if it is not drawn
how to calc current passing through the cell
to calc. current passing through the cell, calc total resistance. Don’t forget to add on the internal resistance
cell current = emf / total resistance
how to work out the current and pd for each resistor
to work out current and pd for each resistor, start with resistors in series with the cell which therefore pass the same cell current
pd across each resistor in series with the cell = current x the resistance of each resistor
to work out the current through parallel resistors
to work out the current through parallel resistors, work out the combined resistance and multiply by the cell current to give the pd across each resistor
current through each resistor = pd across the parallel combination / resistror’s resistance
How is current through the cells calculated in seriues?
dividing the overall emf by the total resistance
The net emf is equal to…
if the cells are connected in the same direction as teh circuit - the sum of individual emfs
if the cells are connected in opposite direction - net emf is teh difference between the emfs in each direction
How is current calculated for identical cells in parallel?
current through each cell = I / n
n = number of identical cells
What the lost pd in each cell for identical cells in parallel?
= (1 / n)r = Ir / n
where r is the internal resistance
What is the terminal pd across each cell for identical cells in parallel?
V = emf - Ir / n
