in this short presentation we're going to look at series connected resistors and link into
Ohm's Law if the multimeter shown was set to measure resistance therefore sets at ohms and
we measured the resistor to have a resistive value of 10 ohms and then we were to apply
a voltage across that resistor of say 60 volts and reset the multimeter now to measure current
it would work out the calculation which we've obtained Ohm's law so current equals voltage
divided by resistance therefore the 60 volts applied across the resistor divided by the 10
ohms of resistance which our current of six amps we have now added a second resistor and
have two resistors connected in series the total resistance in a series circuit is the
sum of the individual resistors so if we label them R1 and R2 the total resistance RT equals
R1 plus R2 if both resistors were of 10 ohms are suggested in the first part of the presentation
the total resistance in circuit would be 10 plus 10 giving you a total resistance of 20 ohms if we
applied the same voltage as previously stated of 60 volts and set the multimeter to measure
current it would work out the calculation of Ohm's law current equals voltage divided by
resistance in this case total resistance so the current in circuit would be 60 volts divided by
20 ohms giving you a circuit current of 3 amps in a series circuit current is common to all parts
of the circuit therefore 3 amps will flow for a resistor 1 and resistor 2 we can go on and work
out the potential difference or voltage that would appear across each of the resistors as
both resistors are valued the same at 10 ohms we would only need to work out the value of voltage
across one of the resistors in order to find out what there would be across both again using
Ohm's law we know the circuit current is 3 amps and we know the value of resistor 1 is 10 ohms
therefore we can do V equals I times R therefore the voltage across the resistor 1 is 3 times 10
the voltage across resistor 1 is 30 volts the second resistor is valued the same therefore
we wouldn't need to calculate that one but we could if it was different and therefore add the
two together to give us our total voltage so if 30 volts appears across resistor 1 and they're
both of the same value 30 volts in this case would appear across resistor 2 giving us a total
voltage of the supply voltage of 60 volts if we had three resistors connected in circuit and we
set a multimeter to measure resistance it would measure the total circuit resistance if each of
the individual resistors were rated at 10 ohms of state in the first part of the presentation the
total resistance in circuit would be 10 plus 10 plus 10 giving you a total resistance of 30 ohms
for this circuit if we once again apply a voltage of 60 volts to these 3 10 ohm resistors connected
in series and change our multimeter to measure current it will do the Ohm's law calculation
for us it would do I equals V divided by R so current is found by voltage divided by total
resistance therefore current equals 60 divided by 30 in other words the current equals 2 amps
once again the potential difference or voltage that appears across each of the resistors can
also be worked out we know the circuit current is 2 amps we know the value of resistor 1 2 & 3
are equal at 10 ohms each so we'll only have to work this out once and add these voltages together
so if we do the voltage V equals current times resistance or I times R we would do 2 times 10
to equal 20 volts appearing across resistor 1 as a resistor 2 & 3 are a recall value of
resistance they also would have 20 volts appearing across those we add them together we get the total
voltage to total voltage would be 20 plus 20 plus 20 giving us our supply age of 60 volts