current, potential difference, power and resistance Flashcards
what are voltage dividers used for?
to set an input voltage to a control circuit
what are potential dividers?
simple series circuits with two or more resistors. the bigger resistor will have a bugger potential difference across it.
how to work out potential difference across resistor
could calculate current flowing in circuit (Vs/RT) then voltage across resistor V=IR2
easier to use equation V1=(R1/R1+R2) Vs
ratio of resistance R1:R2, voltage…
splits in same ratio
rule for current in series
same at all points
rule for current in parallel
sum to supply current
rule for voltage in series
sum to supply voltage
rule for voltage in parallel
same at all points
power definition
the energy transferred every second
power equations
P=IV
P=I squared R
P= V squared / R
measuring resistance using ammeter/voltmeter involves some error unless…
resistance of meters is taken into account
only situation where errors with using ammeter/voltmeter don’t matter is…
if the reading on the meter is zero
Wheatstone Bridge Circuit
-the voltmeter forms a ‘bridge’ between the two voltage dividers to make up a bridge circuit
no potential difference will exist across AB when…
R1/R2 = R3/R4
if Voa=Vob…
there is no potential difference between A and B so no current flows
