Aim:
To verify that in a series circuit; The total resistance is equal to the sum of the
individual resistors.
Apparatus:
● Voltage dc supply, two resistors 100 and 80 Ω, two multimeter,
connection wires.
Background:
Components of an electrical circuit or electronic circuit can
be connected in many different ways. The two simplest of these are
called Series and parallel and occur frequently. Components
connected in series are connected along a single path (figure 1), so
the same current flows through all of the components. Components
connected in parallel are connected, so the same voltage is applied
to each component. A circuit composed solely of components
connected in series is known as a series circuit. In a series circuit,
the current through each of the components is the same, and the
voltage across the circuit is the sum of the voltages across each
component.
Consider a very simple circuit consisting of four light bulbs and one 6 V
battery. If a wire joins the battery to one bulb, to the next bulb, to the
next bulb, to the next bulb, then back to the battery, in one continuous
loop, the bulbs are said to be in series.
Thus,
I total = I1 = I2= I3 ……… (1)
V total= V1+ V2 + V3 …… (2)
R total= R1+ R2+ R3…... (3)
Method:
1. Measure the actual value of the resistors R1 and R2 and record the
result in Table 1.
2. Connect the circuit as in Figure 1 with R1= 80 Ω and with R2= 100 Ω in
Series circuit.
3. Beginning at 10 volt, increase the voltage across R1 and R2 until 20
Volts. Measure and record the resulting current in Table 1 for each
increment of voltage.
4. Plot the graphs with V (y- axis) verses I (x- axis) for results in Table 1.
5. Construct a right triangle on the graph and from this, re-determine the
slope and hence evaluate the resistances.
6. Compare these experimentally obtained values with those measured
values recorded in the respective tables.
7. calculate the error percentage for two resister values from the formula
below:
Error percentage = theoretical value- practical value/
theoretical value * 100 %.