ACTIVITY
SECTION A
(WRITE ACTIVITY OF SECTION A FIRST, FOLLOWED BY EXPERIMENT OF
SECTION A, ACTIVITY OF SECTION B AND EXPERIMENT OF SECTIONB.)
ALL DIAGRAMS MUST BE ON THE FIRST LEFT (BLANK) PAGE AND
OBSERVATION TABLES ON THE RIGHT PAGE.
1
ACTIVITY a1
Aim: To measure resistance, voltage (AC/DC) and check continuity of a given circuit using
multimeter.
Apparatus: three carbon resistors and one standard resistance coil, battery eliminator, step
down transformer, plug key, connecting wires and multimeter.
Theory:
RESISTORS
Carbon resistors are made from mixtures of carbon black, a conducting material and clay and
resin as binder which is a non conductor. The resistivity of the mixtures is governed by the
relative proportion of carbon black. The value of the carbon resistors are indicated by coloured
bands. The colour code and its accuracy are given below.
(Write the colour code table on the blank page)
DC/AC voltage
DC voltage is the voltage of constant magnitude and sign. A battery eliminator is an example of
a source of DC voltage.
AC voltage is the voltage which varies continuously in magnitude and periodically in sign.
Domestic power source is an example of ac voltage .A step down transformer connected to the
mains acts as a source of alternating voltage.
CONTINITY OF A CIRCUIT
A circuit continuous when there is no break in the connecting wires so that current can flow. A
circuit is not continuous if there is break somewhere in the connecting wires or some
component of the circuit may not to be functioning or it may be burnt out.
MULTIMETER
A millimeter is an instrument used for measuring the current, voltage (AC/DC) and resistance.
Principal:(a) Voltmeter: A micro ammeter which makes a full scale defection for 250uA current and with
a coil of resistance 200  can measure up to 50 mV potential differences directly. In order to
2
measure higher potential difference, different high resistances are connected in series with the
micrometer, which can be selected by a rotary knob.
(b) Ammeter: the given micrometer can be used for measuring the higher ranges of current, if
provided with suitable values of shunt in parallel with the coil of the micrometer. Different
values of shunts are provided which can be selected by rotary knob.
(c) Resistance measurement: A variable resistance R, called the “zero adjust” is connected in
series with the coil of the micro ammeter. The probes, when shorted, complete the circuit and
R is adjusted to get the full scale deflection. When the unknown resistance R is inserted in
between the probes, the meter shows reduced deflection due to decrease in current and value
of R is directly read on the scale.
Caution: When using multimeter, plug in connector for right test lead [black (negative) and red
(positive)] use selector switch to right parameter and never exceed the protection limit
indicated in specifications for each range of measurement.
Diagram:
OBSERVATIONS:
(a) for measurement of resistance
S.
No.
Resistor
used
Colours and codes
of rings
1
1
R1
2
3
R2
R3
2
3
Value of resistance
along with
tolerance from
colour code(ohm)
Value read by
multimeter
(ohm)
% difference
4
(b) For measurement of voltage
AC or
DC volts
AC
S. No.
Voltage marked on
supply
V0
(volts)
Voltage reading as
measured by
multimeter
V (volts)
1
2
3
3
Difference in
voltage read and
voltage marked
V – V0 (volts)
DC
1
2
3
(c) For continuity check
S. No.
1
2
Connection
between the
given points
multimeter reading
(ohms)
continuous
open
Conclusion
1. The resistance values measured by multimeter match with decoded values of resistors.
2. AC and DC source voltages match with voltages measured by multimeter.
3. Continuity between given points have been established.
Precautions:
1. Instructions for handling the multimeter should be read very carefully before
performing the activity as it is a very sensitive instrument and is likely to get damaged
out of ignorance or if used carelessly.
2. Be careful to set the selector knob on appropriate parameter i.e. current, voltage or
resistance to be measured and on appropriate range.
3. If range of the parameter under measure is not known, start with the maximum. For
measuring voltage, never connect more than 600V.
Sources of error:
1. AC/DC supply is not regulated.
ACTIVITY a2
Aim: To draw the diagram of the given open circuit comprising of various circuit components.
Mark the components that are not connected in proper order, and draw the corrected circuit
diagram.
Apparatus: battery eliminator, ammeter, voltmeter, rheostat, resistance box, one way key and
connecting wires.
Diagram:
You will be given a wrong circuit. Draw diagram looking at the circuit.
1. The circuit diagram of the given wrong circuit. In the circuit, encircle the components
that are connected wrongly.
2. Then draw the correct circuit diagram.
4
Observations:
S. No.
Faults in the circuit
1.
2.
3.
4.
Keep two lines for each observation.
Conclusion:
The faults in the given circuit have been marked and the correct circuit diagram has been
drawn.
Precautions:
1. Ammeter should always be connected in series and voltmeter should always be connected
in parallel with proper polarities.
2. Correct terminals of rheostat should be connected for offering variable resistances in the
circuit.
3. The circuit should be continuous and at least two terminals of each device should be
connected in the circuit.
ACTIVITY a3
Aim: To study the variation of potential drop with length of wire for steady current.
Apparatus: Battery eliminator, potentiometer, ammeter, voltmeter, rheostat, one way key,
jockey and connecting wires.
Theory:
Principle of potentiometer:
If a steady current is maintained by a battery E, through a wire of homogeneous composition
and uniform area of cross section, then the potential drop V along the wire is directly to its
length.
V∝L
Or, V = kL, where k is the potential drop per unit length and it is a constant. It is called potential
gradient.
Diagram:
5
OBSERVATIONS:
1. No of wires in the potentiometer board
= ……………………………
2. Least count of potentiometer scale
= ……….. cm
3. Source of supply of current to auxiliary circuit
= ……………………..
4. Range of instruments: Ammeter ………… A, Voltmeter ……………. Volt
5. Least count of ammeter
= ………………… A
6. Least count of voltmeter
= ………………. Volt
7. Zero error of ammeter
= ……………….. A
8. Zero error of voltmeter
= ……………….. volt
9. Steady current shown by the ammeter
= ………………… A
Sr. No.
Length of wire
(cm)
Potential drop
(V)
Potential
drop per cm
(volt/cm)
1
2
3
4
5
6
GRAPH: Choose appropriate scale and plot a graph between length(L) on the x-axis and
Potential drop (V) on the y-axis. Find the slope of the graph, after drawing the suitable triangle
on the graph.
CALCULATIONS:
Substitute values from the graph
6
Slope = ΔV / ΔL = (V2 – V1)/ (L2-L1) = k
Therefore, potential drop per cm of the potentiometer wire = …………………….. V/cm
RESULT:
(i) For a steady current, the graph between potential drop V and length L of a conductor is a
straight line. This shows that the potential drop is directly proportional to the length of wire for
a steady flow of current.
(ii)The value of the potential drop per unit length of the wire is ……………. V/cm
PRECAUTION:
1.
2.
3.
4.
5.
6.
All connections should be neat and tight.
The voltmeter should be connected in parallel and the ammeter in series.
The plug in the key should be inserted only while taking observations, otherwise current
would cause unnecessary heating in the circuit.
Zero error in ammeter and voltmeter should be taken into account.
Too high a current should not be drawn from the battery.
It should be ensured that current remains steady throughout the experiment.
7
ACTIVITY
SECTION B
8
ACTIVITY b1
Aim: To identify a diode, a LED, a transistor, an IC(integrated circuit), a resistor and a capacitor
from a mixed collection of such items.
Apparatus: A mixed collection of such items as a diode, transistor, capacitor, resistor and IC.
Diagram:
Theory:
Resistor, capacitor and diode are two terminal devices. A transistor has three terminals and an
IC has a minimum of eight legs. Most of the IC packages have flat back. One can easily
segregate an IC out of a mixture of the above mentioned components. A transistor being a
three terminal device can be identified by just looking at the various components.
For identifying the two terminal devices, the following characteristics of the components may
be utilized.
Resistor: When connected in a dc circuit, it shows a constant current.
Capacitor: When connected in a dc circuit, a multimeter set at R shows initially a full scale
current which decays to zero very quickly.
Diode: Only a diode shows unidirectional flow of current i.e., when connected such that the
terminal end marked P or + is at the higher potential i.e. the diode is forward biased, it
conducts. On reversing the directions, the diode becomes reversed biased and it does not
conduct.
Observation:
Sr. no.
1
2
3
4
5
6
Number of legs (terminals)
More than three
Three
Two
Possible current flow
Unidirectional; emits no light
Unidirectional; emits light
Both directions (steady)
Initially high but decays to zero quickly
9
Device
IC
Transistor
Capacitor, diode or resistor
Device
Diode
LED
Resistor
Capacitor
Conclusion: The components were identified correctly from the given collection.
ACTIVITY b2
Aim: To observe the polarization of light using two Polaroids.
Apparatus: Two Polaroid pieces, a source of light.
Theory:A Polaroid piece allows only that part of light which has electrical vibrations along the
axis of polarization of the Polaroid. It means that after passing through Polaroid, unpolarised
light becomes plane polarized.
If another Polaroid is placed in the path of the plane polarized light so that the two Polaroids
are in cross position then no light will come out of the second Polaroid. If the axes of the two
Polaroids are parallel to each other then the light produced by the first Polaroid is able to pass
through the second Polaroid as shown in the figure.
Diagram:
Observations:
In one position of the two Polaroids, the source of light was found to have maximum
brightness, and in another position obtained by rotating one Polaroid over the other, no light or
very dim light was observed.
Conclusion:
The above activity shows that a Polaroid produces plane (linearly) polarized light. The polarized
light does not pass through another Polaroid when it is placed in crossed position with respect
to the first Polaroid.
ACTIVITY b3
Aim: To observe diffraction of light due to thin slit between sharp edges of razor blades.
10
Apparatus required: A glass plate, two razor blades, adhesive tapes, a screen, a source of
monochromatic light (laser pencil), and black paper.
Theory:
When light is allowed to pass through fine openings or around sharp obstacles like edge of
razor blades such that size of opening or sharpness of edges is of the order of wavelength of
light (≈ 5 x 10 -7 m), it bends around corners and forms alternate dark and light fringes. Bending
of light around obstacles or corner is termed as diffraction and the fringe pattern is called
diffraction pattern. The angle of diffraction for different orders (n) of diffraction is given as d sin
θ=n λ, where d is slit size, θ is diffraction angle, n is order of diffraction and λ is wavelength of
light used.
Diagram:
Observations:
S. No.
Characteristic
1.
Nature of pattern
2.
Intensity variation in bright
regions
Width variation
3.
4.
Observation
Variation in intensity with
distance
Keep two lines space for each observation.
Conclusion:
When light waves are incident on very fine openings they bend and spread showing the
phenomena of diffraction of light.
Precautions:
1. Black paper should be pasted such that there is no air gap between the glass plate and
paper.
2. The slit should be made as thin as possible.
3. Instead of using ordinary electric bulb, laser torch light will give better effect on the screen.
11