Question

Study the table related to combination of resistors and answer the questions that
follow on the basis of your understanding and the related studied concepts.
Circuits consisting of just one battery and one load resistance are very simple to analyse,
but they are not often found in practical applications. Usually, we find circuits where
more than two components are connected together in different combinations. These
combinations of resistors put the limit on the current that flow through the circuit.
After performing the experiments using two different types of circuit arrangement, the
following observations were made by them and find the resistance using Ohm’s law.
Resistor used Number of
Observations

Voltmeter
Reading (V)

Ammeter
Reading (A) R =
V
I
(Ω)

R1

(a)
(b)

0.01
0.02

0.01
0.02

1.0
1.0

R2

(a)
(b)

0.06
0.08

0.03
0.04

2.0
2.0

1
st combination
of R1 and R2

(a)
(b)

0.03
0.06

0.01
0.02

3.0
3.0

2
nd combination
of R1 and R2

(a)
(b)

0.03
0.06

0.045
0.09

0.66
0.66

(a) From observation, which combination represents series and parallel combination of
resistor R1 and R2 ? (1)
(b) You will plot Volt versus Current for each of the four circuits on one graph. What
value should each slope have? (1)

(c) Note that the measured currents across each resistor in parallel circuit were not the
same. Which resistor had larger current going through it? Why?

Answer 1

(a) The 1st combination of R1 and R2 represents the series combination of resistors R1 and R2,

• as the resistance in this combination is the sum of the individual resistances (R1 + R2 = 3.0 Ω).
• The 2nd combination of R1 and R2 represents the parallel combination of resistors R1 and R2, as the resistance in this combination is the reciprocal of the sum of the reciprocals of the individual resistances (1/(1/R1 + 1/R2) = 0.66 Ω).

(b) The slope of the graph for the 1st combination of R1 and R2 should be equal to 3.0 Ω,

• as this represents the resistance in the series combination.
• The slope of the graph for the 2nd combination of R1 and R2 should be equal to 0.66 Ω, as this represents the resistance in the parallel combination.

(c) The resistor R2 has a larger current going through it in the 2nd combination of R1 and R2.

• This is because in a parallel circuit, the current is divided between the two resistors in proportion to their individual resistances.
• Since R2 has a higher resistance than R1, the current going through R2 will be less than the current going through R1.

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Answer 2

Answer:

(a) The 1st combination of R1 and R2 represents the series combination of resistors R1 and R2,

• as the resistance in this combination is the sum of the individual resistances (R1 + R2 = 3.0 ).

The 2nd combination of R1 and R2 represents the parallel combination of resistors R1 and R2, as the resistance in this combination is the reciprocal of the sum of the reciprocals of the individual resistances (1/(1/R1 + 1/R2) = 0.66 N).

(b) The slope of the graph for the 1st combination of R1 and R2 should be equal to 3.0 Q,

as this represents the resistance in the series combination.

The slope of the graph for the 2nd combination of R1 and R2 should be equal to 0.66 Q, as this represents the resistance in the parallel combination.

(c) The resistor R2 has a larger current going through it in the 2nd combination of R1 and R2.

This is because in a parallel circuit, the current is divided between the two resistors in proportion to their individual resistances.

Since R2 has a higher resistance than R1, the current going through R2 will be less than the current going through R1.