CLASS 12 ACTIVITY COPY 2022-2023

SECTION A
ACTIVITY 1

AIM: To assemble the components of a given electrical circuit.

APPARATUS AND MATERIAL REQUIRED

Resistor, ammeter, (0-1.5A) voltmeter (0-5V), battery, one way key, rheostat,
sand paper, connecting wires.

DIAGRAM: ( DRAWN ON LEFT SIDE)

PROCEDURE

1. Connect the components as shown.

2. After closing the key K, check that the voltmeter and ammeter show
deflections on the right hand side.

3. Check the continuity of the assembled circuit using a multimeter.

4 The ammeter should be connected in series with the resistor and the
voltmeter should be connected in parallel with it.
5 Voltmeter and ammeter of suitable range should be chosen.
6 Ammeter should always be connected in series and voltmeter should
always be connected in parallel with proper polarities.
7 Rheostat should be connected carefully selecting the correct terminals only.

RESULT

The components of the electrical circuit were assembled.

PRECAUTIONS

1 The positive terminal of the battery should be connected to the

positive terminal of ammeter and positive terminal of the voltmeter.

2. The ammeter should be connected in series with the resistor and the
voltmeter should be connected in parallel with the resistor.

3. Sand paper should be used to clean the ends of connecting wires

and leads of the component terminals. Grease/oil or oxide layer on their

surfaces is insulating in nature and needs to be removed.

However, do not clean the plugs and keys with sand paper.Excessive use of
sand paper in such a case will make the plug unfit to be used with the key

ACTIVITY 2

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.
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.
CONTINUITY 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.

(a) Voltmeter: A micro ammeter which makes a full scale defection for
250uA current and with a coil of resistance 200Ω can measure 50 mV
p.d. directly.
 Observations( for resistance measurement)
S no Colour code Colour coded value Experimental
value

1 Green ,Violet, 57x100 OHMS, 20 % 5679 OHMS

Red

2 BROWN , 1000 OHMS, 5 % 960 OHMS

BLACK RED
, GOLD

3 ORANGE , 32 KILO OHMS, 10% 3.16 KILO OHMS

RED,
ORANGE,
SILVER

Observations ( for voltage measurement)

S no Voltage mentioned on cell/eliminator Experimental value

1 1.5V 1.45V

2 2V 1.8 V

3 4V 3.7V

Conclusion:
The multimeter was used for measurement of voltage, resistance and
checking continuity of the circuit.
 ACTIVITY 3

Aim: To study the variation of potential drop with length of wire for a steady
current.
Apparatus: A potentiometer, battery accumulator, plug key, dc voltmeter,
connecting wires
Theory:
Potentiometer: It is an instrument which is used for the measurement of
potential drop and emf of a cell
If a steady current is maintained by a battery e, through wire of
homogeneous composition and uniform cross section, then the potential drop
V along the wire is directly proportional to its length, i.e.
Vαl
V/l = k (constant)
Where k is the drop of potential per unit length. It is called potential gradient

Diagram: DRAWN ON LEFT SIDE

PROCEDURE
1 Set up the electrical circuit as shown.
2. ow close the key K and press the jockey at point B. Adjust the rheostat to
get full scale deflection in voltmeter.
3. When jockey is pressed at point A, you will get zero deflection in the
voltmeter.
4. Now press the jockey at 40 cm and note the corresponding voltmeter
reading.
5. Repeat your observation by pressing the jockey at various lengths like 80
cm, 120 cm etc. which may extend upto, say 400 cm of potentiometer wire.
Record voltmeter reading in each case

OBSERVATIONS
S no L(in cm) V(in volts)
1 50 cm 0.25 V
2 100 cm 0.5 V
3 150 cm 0.75 V
4 200 cm 1.0V
5 250cm 1.25 V
6 300cm 1.5V

Graph: Choosing a suitable scale, plot a graph of potential drop V along y-

axis corresponding to values of length l, along x-axis.
Calculations:
From the graph, the slope = (V2 – V1)/ (L2 – L1)
Slope = potential gradient =∆V/∆L =0.25V/50cm=0.005 V/cm
Conclusion:
(i) For a steady current (…..A), the graph of V vs L is a straight line. This
shows
that potential drop is directly proportional to the length for a steady flow of
current.
(ii) The potential gradient is…0.005 V/cm -V/cm.

Precautions
1 Current should not be passed for along time
2 Jockey should not be dragged on the wire
Activity 4

Aim: To identify a diode, a LED, a resistor and a capacitor from a mixed

collection of such items.
Apparatus: A mixed collection of such items as a diode, LED, capacitor,
resistor.

Theory: Resistor, capacitor and diode are two terminal devices.

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.
LED : When a LED is connected such that the terminal end marked P or + is
at the higher potential i.e. the diode is forward biased, it glows. On reversing
the directions, the diode becomes reversed biased and it does not glow.

DIAGRAMS (DRAWN ON LEFT SIDE)

Possible current flow Device
4 Unidirectional; emits no light Diode
5 Unidirectional; emits light LED
Both directions (steady) Resistor
6 Initially high but decays to zero quickly Capacitor

Conclusion: The components were identified correctly from the given

collection.

ACTIVITY 5
Aim : To obtain a lens combination with the specified focal length by using
two lenses from the given set of lenses.

Apparatus: A set of convex lenses, a meter scale.

DIAGRAM

Theory
Consider two lenses A and B of focal length f1 and f2 placed in contact with
each other. Let the object be placed at a point O beyond the focus of the first
lens A .The first lens produces an image at I1. Since image I1 is real, it serves
as a virtual object for the second lens B, producing the final image at I. It
must, however, be borne in mind that formation of image by the first lens is
presumed only to facilitate determination of the position of the final image.
In fact, the direction of rays emerging from the first lens gets modified in
accordance with the angle at which they strike the second lens. Since the
lenses are thin, we assume the optical centres of the lenses to be coincident.
For the image formed by lens A, we get

For the image formed by lens B, , the virtual image formed at I1 acts as the
object, thus for lens B, u = v1 and we get

Adding equation (1) and (2), we have

Or

Where f is the effective focal length of the combination of the lenses.

Or

The formula is valid for any number of thin lenses in contact. If a number of
lenses are in contact, then

The effective power of the combination is

P = P 1 + P2 + P3 + P 4 + … . . . . . . . .
PROCEDURE

1 Measure the rough focal length of both the lenses individually by focusing
them on a wall.
2 Now hold both of them together and measured their combined focal length
similarly.
3 Record your observations.
4 Calculate the combined wavelength using the formula given above.

Measured Focal Effective Theoretically

length of the focal obtained
S. No.
lenses length focal
(cm) (cm) length(cm)
f1 f2 f F
1 20cm 10cm 7cm 6.66cm
2 15cm 10cm 6.2 cm 6cm

Result
There is a close agreement between the experimentally and the theoretically
obtained values of combined focal lengths of the two lenses.

Precautions
1 Parallax error should be avoided.
2 The meter scale should be held horizontally.

ACTIVITY 6
Aim: To observe refraction and lateral deviation of a beam of light incident
obliquely on a glass slab.

Apparatus required: Drawing board, rectangular glass slab, white sheet of

paper, adhesive tape (cello-tape), drawing pins, a metre scale, alpins,
protractor, sharp pencil and eraser

Theory:
When a ray of light is incident on a rectangular glass slab, it is
refracted through it. It emerges out of the slab parallel to the
direction of the incident ray. The emergent ray suffers only a lateral
displacement. For a given angle of incidence and a pair of media, the lateral
deviation is proportional to the thickness of the glass slab.
DIAGRAM

PROCEDURE
1 Fix a white sheet of paper on the drawing board with the help of drawing
pins.
2. Place the glass slab lengthwise symmetrically at the centre of the paper
sheet and mark its boundary ABCD on the paper sheet with a sharp pencil.
3. Draw a normal at a point F on the face AB. Draw a line EF,representing
the incident ray, making an angle i the angle of incidence with the normal.
4. Fix two alpins P and Q with sharp tips, about 8 to 10 cm apart,
vertically on the line EF.
5. Observe the images of the two pins through the face opposite of the glass
slab. Fix two more alpins R and S about 8 to 10 cm apart, vertically on the
white paper sheet carefully with their tips in line with the tips of the images
of P and Q.
6. Remove the glass slab and draw a straight line GH, representing the
emergent ray, passing through the points marked R and S, meeting the face
CD at G.
7. Draw the line FG to represent the refracted ray. Draw a normal at the
point G on the face CD; making an angle of emergence e with the normal.
Measure the angle of incidence i and angle of emergence e with a protractor.

8. Determine the lateral shift using a scale

9 Repeat steps 2 to 9 by changing the angle of incidence and thickness of slab
Observations
SNO THICKNESS ANGLE OF ANGLE OF LATERAL
OF SLAB INCIDENCE EMERGENCE SHIFT
1
2

Conclusion:
The ray of light emerging from a glass slab is parallel to the incident ray
direction, but is laterally deviated.
2. The lateral deviation of the emergent ray with respect to the
incident ray is directly proportional to the thickness of the
glass slab.

Precautions:
1. Parallax errors should be avoided
2. Pins should be straight

Or
ACTIVITY 6
Aim: To observe diffraction of light due to thin slit between sharp
edges of razor blades.

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
dsinθ=nλ

Observation: A diffraction pattern was obtained in which

secondary minimas were obtained alongside the bright maxima.

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