Activities
Activity -1
Aim of the activity:- To measure resistance, voltage(ac/dc), current (a.c.) and check continuity of a given circuit using
multimeter.
Apparatus :-
1. Three carbon resistors
2. One standard resistance coil
3. A battery eliminator with tapping (2 V, 4 V and 6 V),
4. A step down transformer (6-0-6 V) with two tapping (2 V and 4 V),
5. A resistor of 100 ohm
6. A One way key and Connecting wires
7. Multimeter.
Diagram :-
Theory:-
Multimeter:- It is an instrument used for measuring current(a.c./d.c.) , voltage (a.c./d.c.) and
resistance. It is single measuring device acting as an Ammeter, a Voltmeter and an Ohmmeter. For
this reason, it is also called AVO meter.
It can measure alternating as well as direct current and alternating as well as direct voltage in addition
to resistance. For this purpose its panel is divided into five different sections. There are many ranges
in each section so that it can measure from micro (10 -6) to mega (106) units. Rotation of a knob
changes the section and the range in one section.
— Rotation of knob for change in ammeter range, brings shunt resistances of different values in circuit in
parallel with the coil.
— Rotation of knob for change in voltmeter range, brings series resistances of different values in circuit in
series with the coil.
— Rotation of knob for change in ohmmeter range, brings different resistances in circuit in series with the
multimeter cell.
1. Carbon resistors are frequently used in electrical and electronic circuits and their values vary
over a very wide range. A colour code is used to indicate the value of the resistance.
2. A carbon resistance has four different concentric coloured ringe or bands on its surface. The
first three bands a, b and c determine the value of the resistance and the fourth band d gives
the percentage of accuracy called tolerance. The resistance of carbon resistor R = (ab x 10 c ± T
%) Ω.
3. The following table provides the colour code for the carbon resistors :
Letter Colour !st Band 2nd Band 3rd Band multiplier (c) 4th band
(a) (b) Tolerence (T)
1 B Black 0 0 X1 Ω 100
2 B Brown 1 1 X10 Ω 101 ±1 %
3 R Red 2 2 X100 Ω 102 ±2 %
4 O Orange 3 3 X1 KΩ 103
5 Y Yellow 4 4 X10 KΩ 104
6 G Green 5 5 X100 KΩ 105 ±0.50 %
7 B Blue 6 6 X1 MΩ 106 ±0.25 %
8 V Violet 7 7 X10 MΩ 107 ±0.10 %
9 G Grey 8 8 X100 MΩ 108 ±0.05 %
10 W White 9 9 X1 GΩ 109
11 Gold X0.1 Ω 10-1 ±5 %
12 silver X0.01 Ω 10-2 ±10 %
Procedure
1. Mark the given carbon resistors as R1,R2, R3.
2. Note the colour of first, second, third and fourth ring for each resistor.
3. Plug in the probes of the multimeter in appropriate terminals. Select the appropriate range, short
the other ends of probes and adjust zero. Turn the terminal marked ‘Adjust’ such that the needle
of the meter shows full scale deflection and reads zero ohm.
4. Separate the metallic ends of the probes. Insert the resistor R 1 to be measured in between the
metallic ends of the two probes and read the deflection of the pointer on the range selected.
5. Repeat the step 4 for other resistors R2and R3 each time selecting the appropriate range and
testing the zero.
6. Now convert using the colour code table, the values of resistors in ohms and write their values
with tolerance.
(b) D.C. Voltage
1. Select a D.C. source of potential difference, 6 V battery eliminator or a battery.
2. Plug the probes black in com and red in +.
3. Select D.C. volt, by turning the selector switch to range 10 V D.C. volts,
4. Touch and press other ends of probes such that red is on battery terminal marked + and black
on and not the reading.
5. Insert red probe in terminals marked 4 V, 2 V in succession and note readings.
(c) A.C. Volts
1. Turn the selector A.C. (200 Volt).
2. Touch and press the probes other ends to two terminals of A.C. source of potential
drop and note the reading.
3. Use red probe in terminals 4 V and 2 V in succession and record the reading.
(d) Continuity of given circuit
1. Set the selector switch to ohm, range MΩ.
2. Touch and press the ends of probes at A and B, full scale deflection indicates continuity.
3. Similarly check in succession the continuity between terminals B and C and terminals C and D.
Never place the probes ends between terminals connected with the terminals of the battery.
In digital electronic multimeter for continuity test rotor is set to mark 0 and a buzzer , sounds
when probes are connected to ends of components tested.
Observation table:-
Table-1:-
Values and Value by %
Resistors Colour code of rings tolerance from multimeter differences
used colour code (Ω) (Ω) =
1 st ring 2nd ring 3rd ring 4th ring (R1) (R) 𝑅−𝑅1
( )x100
𝑅
R1 brown black brown golden 100 ± 5 % 100.5 .5 %
R2 brown black red golden 1000 ± 5 % .991k .9 %
R3 brown black orange golden 10000 ± 5 % 9.73k 2.7 %
Table-2:-
No. of Output voltage marked on Voltage as measured by Differences % differences
observation battery eliminator (V0) in multimeter (V) in volt V ~ V0 𝑉−𝑉
=( 𝑉 0 ) 𝑥100
volt
1 2 2.28 .28
2 4 4.16 .16
3 6 5.98 .02
Table-3:-
No. of Output voltage marked on Voltage as measured by Differences % differences
observation transformer (V0) in volt multimeter (V) in volt V ~ V0 𝑉−𝑉
=( 𝑉 0 ) 𝑥100
1 6 6.9 0.9
2 8 9 1
Table-4:-
No. of Resistance used from Reading of the Reading of actual Differences
observation resistance box R(ohm) multimeter ( 𝐼 ) in milli-ammeter ( 𝐼′ ) ( 𝐼 ~𝐼 ′ )
mA
1 2 1 1 0
2 4 1.5 1.5 0
Result :-
1. Within the experimental error limits(within allowed experimental error limits) the values of the carbon resistor
calculated by colour coding and measured with the help of multimeter is same.
2. Voltage (AC/DC) measured by multimeter is nearly same as the value of voltage marked on (Ac/Dc) source.
3. Since, the multimeter shows zero (or infinite) resistance ,hence ,the given circuit is continuous (or
discontinuous).
Precaution :-
1.multimeter should not be used carelessly otherwise it may get damaged, red the instruction before its use.
2. pass the alternating current for maximum possible time.
3. In measuring Ac voltage/Current ,polarity probe leads should be connected to the proper polarity in the
circuit.
4. If range of resistance,voltage or current to be measured is not known ,start with the maximum range and
then go on decreasing the range till suitable deflection is obtained in the multimeter.
Activity -2
Aim of the activity :- To assemble a household circuit comprising three bulbs, three (on/off) switches,a
fuse and a power source.
See the video link :- https://youtu.be/J8cKCdaPnlM?si=nfEuuBm1C8-YVTlc
Or you can follow your book. Activity section A.
Result:-
from the above activity,we assemble a house hold circuit comprising three bulbs,three switches, a fuse and
a power source , when switch is on the bulbs glow and switch is made IOFF , the bulb stops glowing. Hence
circuit is working perfectly.
Activituy -3 :- To assemble of a given electrical circuit.
Activity –4:-
Activities
(Section – B)
Activity-1
Activity –2
Activity –3
Activity –4
s.i Position of Position of candle (cm) Position of Size of image Relative size of
no convex image (cm) (cm) the image w.r.t.
lens (cm) object
1 35 At infinity 21 0.4-0.5 Very Small
( 100)
2 35 Beyond 2F 8.5 1-1.5 Small
(65)
3 35 At 2F 07 3 Equal
(63)
4 35 Between F and 2F 03 4-4.5 Larger
(60)
