Download L4 series and parallel resistors

TITLE:
Resistors in series and parallel and power measurement conductance
OBJECTIVE:
To verify the formulae for resistors in series and parallel. Calculate power
from measurements of voltage and current
EQUIPMENT:
Variable voltage d.c. power supply, switch, resistors, circuit board.
THEORY:
When resistors are connected in series the total resistance of the circuit is given by the
formulae: Rtot = R1 + R2 + R3 …… Ohms.
When resistors are connected in parallel the total resistance of the circuit is given by the
formulae: 1/Rtot = 1/R1 + 1/R2 +1/R3….. Ohms.
The effect of current flowing through a resistor generates heat (electric to heat energy conversion)
Power P = V∙I Watts (W)
Resistance = V/I Ohms (Ω)
PROCEDURE:
Figure 1
A
Ammeter
Variable voltage
d.c. supply
Voltmeter
V
R
Resistors in series:
Figure 2 Resistors in series
I
R1
R2
R3
V1
V2
V3
V
Rtot = V/I
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
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
Replace R in the circuit shown in Figure 1 with three resistors in series as shown in Figure 2,
Determine the nominal value of the resistors (RN) provided from their colour code.
Set the supply voltage so that there is a 10 V across the three resistors.
Measure the total current I flowing in the circuit with the ammeter and the voltage across
each resistor. Place the results in Excel worksheet as shown below.
Calculate the each and total resistance from Ohms Law.


R
R1
R2
R3
RSer
Compare this to the theoretical formulae calculation to confirm formulae for resistors in
series and calculate percentage error between values.
Calculate power dissipated by each resistor and total resistance using current measurement
and resistance voltage measurements
RN (Ω)
VR (V)
IR(mA)
Rexp (Ω) Err.(%)
PR (mW)
10
Resistors in parallel:
Figure 2 Resistors in parallel
I
I1
I2
V






R2
R1
I3
R3
Rtot = V/I
Replace R in the circuit shown in Figure 1 with three resistors in parallel as shown in Fig.3.
Set the supply voltage so that there is a 3 volt p.d. across the parallel network of resistors.
Measure the total current I flowing in the circuit and the currents flowing in each branch
with the ammeter. Place the results in Excel worksheet.
Calculate the each and total resistance from Ohms Law.
Compare this to the theoretical formulae calculation to confirm formulae for resistors in
parallel and calculate % error between values.
Calculate power dissipated by each resistor and total network using the supply voltage and
current measurements.
Series - Parallel Circuit
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
Repeat the experiment with a combination of 5 resistors connected as shown.
Note: V= V1+V3, I=I1+I2= I3+I4 and V1=V2, V3= V4+V5, I4= I5
I1
I
I2
R1
R3
I3
V3
V1
R2
R4
R5
V2
I4 V4
V5