Phy Practical Activities Format

CIPHER COMPUTER CLUB

PHYSICS PRACTICAL ACTIVITIES Compiled and distributed by:

CIPHER COMPUTER CLUB 1 PDF Created with deskPDF PDF Writer - Trial :: http://www.docudesk.com

CIPHER COMPUTER CLUB

Special Thanks Mrs. Pragya Nopany Maam

Contributed by:Aneesha Chandra Published and edited by: Mukul Gupta

Introduction: This publication provides you with the prescribed format of all the activities to be performed during PHYSICS PRACTICALS as to be written in the PRACTICAL FILE. Note:It does not provide you with any experimental data whatsoever. All the observation tables,calculations,Result etc. will have to be inputed as performed during the practicals.

2 PDF Created with deskPDF PDF Writer - Trial :: http://www.docudesk.com

CIPHER COMPUTER CLUB

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 Ω can measure 50 mV p.d. directly. In 3 PDF Created with deskPDF PDF Writer - Trial :: http://www.docudesk.com

CIPHER COMPUTER CLUB order to measure higher p.d. 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: (1) page 134 fig. 7.2 (2) page 138 fig. 7.5 OBSERVATIONS: (a) for measurement of resistance Resistor used

Colours and codes of rings

1

2

3

Value of tolerance from colour code(ohm)

Value of multimeter (ohm)

% difference

4

R1 R2 R3

(b) For measurement of voltage AC or DC volts

S. No.

Voltage between terminals Vo (volts)

Voltage reading as measured by multimeter V(volts)

Difference in voltage read and voltage marked V – Vo(volts)

1

4 PDF Created with deskPDF PDF Writer - Trial :: http://www.docudesk.com

CIPHER COMPUTER CLUB AC

2 3 1 2

DC 3

Conclusion 1: The measured values by millimeter match with decoded values of resistors. 2: AC and DC voltages sources match with voltage measured by multimeter. Precaution: (Write precautions as given in the book)

ACTIVITYa2 Aim: To assemble the components of the given electrical circuit. Apparatus: electrical components like resistor, battery, ammeter, voltmeter, plug key, galvanometer, Meter Bridge, rheostat, connecting wires. Diagram: Ckt 1: Ohm’s law Ckt 2: meter bridge to find unknown resistance Ckt 3: potentiometer to compare emfs

Conclusion: Assembly of all components in all the electrical circuits are complete.

Precaution: 1. All components are connected in series with each other. 2. Ammeter is always in series and voltmeter is always connected in parallel. 5 PDF Created with deskPDF PDF Writer - Trial :: http://www.docudesk.com

CIPHER COMPUTER CLUB 3. Red terminals of ammeter and voltmeter, marked positive should be connected in the circuit towards the positive terminal of the battery and their black terminals, marked negative should be connected towards the negative terminal of the battery.

ACTIVITY a3 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 Principle: 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. V l V/l = k (constant) where k is the drop of potential per unit length. It is called potential gradient Diagram: page 144/fig. 7.9 (correction in the circuit i) the device in the lower circuit is voltmeter and not galvanometer and ii) the polarity of the ammeter should be opposite to that as given in the circuit.) OBSERVATIONS 1. No. of wires on the potentiometer board = …………………………… 2. Range of the voltmeter = ……………………………… 3. Range of ammeter = ……………………………… 4. Least count of voltmeter = ……………………………… 5. Least count of ammeter = ……………………………… 6. Steady current shown by ammeter = ……………………………… S.No. Steady Length of wire Potential drop Potential drop per cm L for steady V/L Current I (cm) current I (volt/cm) (A) V (volt) 6 PDF Created with deskPDF PDF Writer - Trial :: http://www.docudesk.com

CIPHER COMPUTER CLUB 1

40

2

80

3

120

4

160

5

200

6

240

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 = ………………… 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 ………… V/cm. Precaution: (as given in the book) ACTIVITY a4 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: 1. The circuit diagram of the given wrong. In the circuit encircle the components that are connected wrongly. 2. The correct circuit diagram. 7 PDF Created with deskPDF PDF Writer - Trial :: http://www.docudesk.com

CIPHER COMPUTER CLUB Observation: S.No.

Faults in the circuits

1. 2. 3. 4. Conclusion: The faults in the given circuit were corrected and the correct circuit diagram was drawn. Precautions: 1. Voltmeter and ammeter of suitable range should be chosen. 2. Ammeter should always be connected in series and voltmeter should always be connected in parallel with proper polarities. 3. Rheostat should be connected carefully selecting the correct terminals only.

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. 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. 8 PDF Created with deskPDF PDF Writer - Trial :: http://www.docudesk.com

CIPHER COMPUTER CLUB 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. Number of legs (terminals) 1 More than three 2 Three 3 Two Possible current flow Unidirectional; emits no light Unidirectional; emits light Both directions (steady) Initially high but decays to zero quickly

4 5 6

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 refraction and lateral deviation of a beam of light incident obliquely on a glass slab. Apparatus: glass slab drawing board, white sheet of paper, board pins etc. Theory:

9 PDF Created with deskPDF PDF Writer - Trial :: http://www.docudesk.com

CIPHER COMPUTER CLUB If a ray of light travelling from air enters a glass slab, its velocity changes; either in speed or in direction or both. Since it is moving from rarer to denser medium, it bends towards the normal. The angle of refraction ® will be less than the angle of incidence (i). When it reaches the other face of the glass slab, it suffers another refraction but from denser to rarer medium this time. So, it bends away from the normal and emerges from the other face. The angle made by this emergent ray with the normal is called angle of emergence. The emergent ray is found to be parallel to the original ray, and there is a lateral deviation between the two rays. This deviation depends upon the thickness of the glass slab among other factors. Diagram: fig. 11.8 on page 249

Observation: On the white sheet mark the deviations observed in the glass slab for three different positions of the slab but for the same angle of incidence for all three. Sr.No. 1. 2. 3.

Angle of incidence(i) 40 40 40

Angle of refraction(r)

Thickness of slab(cm)

Lateral displacement(cm)

Conclusion: 1. Ray of light emerging from a glass slab is parallel to the incident ray and it is laterally displaced. 2. The lateral displacement of the emergent ray increases with the increase in thickness of slab.

ACTIVITY b3 Aim: To observe the polarization of light using two Polaroids. Apparatus: Two Polaroid pieces, a source of light. Theory: 10 PDF Created with deskPDF PDF Writer - Trial :: http://www.docudesk.com

CIPHER COMPUTER CLUB A Polaroid piece allows only that part of light which has vibrations along the axis of polarization of the Polaroid. It means that unpolarised light after passing through Polaroid piece becomes plane polarized. If another Polaroid piece is placed in the path of the plane polarized light so that the two Polaroid pieces are in cross position then no light will come out of the second Polaroid piece. 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: Fig 11.10(a) and (b) of page 251. 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 at which no light or very dim light was obtained. Conclusion: The above activity shows that Polaroid pieces produce plane (linearly) polarized light. The polarized light does not pass through another Polaroid when it is placed crossed with respect to the first Polaroid.

ACTIVITY b4 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 Diagram: Fig 11.11 on page 252

11 PDF Created with deskPDF PDF Writer - Trial :: http://www.docudesk.com

CIPHER COMPUTER CLUB 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.

END OF PAGE

12 PDF Created with deskPDF PDF Writer - Trial :: http://www.docudesk.com