Questions and answers normally not answered by students in physics

1. Name the Physical quantities to be kept constant for Ohm’s law to be true. 
2. State the Principle of a potentiometer. (The students say that potential drop is proportional to length but the constant quantities are not mentioned) How can we increase the sensitivity of a potentiometer? 
3. Define figure of merit of a galvanometer. Which has more resistance – a galvanometer or a milliammeter? 
4. How does an LED emit light? 
5. What is the difference between an ordinary diode and an LED? 
6. Define principal axis of a convex lens? 
7. What happens to the focal length of a concave mirror if it is immersed in water? 
8. What are the factors affecting the intrernal resistance of a cell? 
9. What are the difference between primary and secondary cell? 
10. Why can’t we use a dry cell for starting a car? 

Hints/Answers 

1. length, area of cross section,temperature 
2. The potential drop across any length of a conductor of uniform cross section and composition carrying a constant current is directly proportional to the length. Increasing the length of potentiometer wire, decreasing the current, decreasing the potential gradient Current for unit deflection galvanometer 
3. The energy released during recombination of electrons and holes across the junction is responsible for the release of light by LED In ordinary diode the energy emitted during recombination of electrons and holes is in the invisible region of the em spectrum but in the case of LED, the energy is in the visible region. 
4. Straight line joining the centres of curvature of the lens.. 
5. The focal length of mirror does not change by changing the medium. 
6. Their is a pure geometrical relationship between the radius of curvature and focal length and the relation does not include any term depending on refractive index. 
7. The nature of electrolyte, the concentration of electrolyte, temperature, distance between electrodes, area of electrodes Primary cell cannot be recharged, secondary cells can be recharged; secondary cells have less internal resistance than primary cells. Due to the high internal resistance of a dry cell, it won’t be able to provide the current sufficient to start the car

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GRAPH DRAWINGS TECHNIQUES

GRAPH DRAWING

INTRODUCTION

Most of practical in physics involves drawing of graphs as a key element in any physics practical

RULES USED IN GRAPH DRAWING

The following are the most important rules required to follow in drawing a graphs.

 i.        Write the heading of your graph on the top of the graph by using capital letter

 ii.      Underline your heading

Eg. THE GRAPH OF L (Cm) VS T² (S²)

iii.    Select the suitable scale and write it below heading to the right hand side.

Eg. SCALE

Vertical   1cm: 2cm

Horizontal 1cm: 0.1s

Note

To present scale always used two ways either in words or ratio not otherwise.

iv.    Draw the horizontal and vertical plane according to the instruction given.

All the line intersed at origin 0.

For example, draw the graph of L (cm) against T2 (S²)

THE GRAPH OF L (cm) Vs T² (S²)

SCALE

Vertical scale 1cm: 2cm

Horizontal 1cm: 0.1s

v.      Locate the coordinate (points) to present the nature of the graph, draw the joining each point on the planes

Eg.

vi.    Determine the slope of the graph selecting any two points on the graph,

     (i.e. A and B)

Slope (M) = change in   L (cm)/ change in T2(S2)

   

Note

Remember to write the SI Units of your slope (M) if possible.

I.e. (Cm/s²)

Determine the x and y intercepts if that is required, from the nature of the graph.

Note

Most practical questions depend on the graph:

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4.0 THE FORMAT OF ANY PHYSICS EXPERIMENTS,

THE FORMAT OF PHYSICS EXPERIMENTS,

The experiments are presented in the form of self-instructional

material in the following format

1) Aim: It defines the scope of the experiment.

2) Objectives: The objectives of an experiment give you an idea about the

skills or the knowledge that you are expected to develop after performing

that experiment.

3) What you should know?: It highlights the concepts and background

knowledge related to the experiment, which you must understand in order

to do the experiment in a meaningful way.

4) Material required: It gives an exhaustive list of apparatus and other material

required to perform the experiment.

5) How to set up and perform the experiment?: The steps are given in a

sequential manner for setting up the apparatus and performing the,

experiment. The precautions, wherever necessary, are incorporated while

describing various steps.

6) What to observe?: A proper format of recording the observations, is

suggested in each experiment.

7) Analysis of data: How to analyze your data, is suggested in each experiment;

Quite frequently, it is combined with the previous heading, at serial number 6.

8) Result: It is the outcome of the observations and supports the aim set in the

beginning.

9) Sources of error: Since all the experiments in physics involve measurements,

your attention; is drawn in each experiment to major pitfalls specific to that

experiment, if any, which may cause error in your measurements.

10) Check your understanding: At the end of each experiment, a few questions

have been incorporated to consolidate what has been done and to check

your own understanding about it.

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3.0 GENERAL INSTRUCTIONS FOR LABORATORY PRACTICALS:

GENERAL INSTRUCTIONS:

1. You must arrive on time since instructions are given and announcements are made at

the start of class.

2. Awork station and lab partners will be assigned to you in the first lab meeting. You

will do experiments in a group but you are expected to bear your share of responsibility

in doing the experiments. You must actively participate in obtaining the data and

not merely watch your partners do it for you.

3. The assigned work station must be kept neat and clean at all times. Coats/jackets

must be hung at the appropriate place, and all personal possessions other than those

needed for the lab should be kept in the table drawers or under the table.

4. The data must be recorded neatly with a sharp pencil and presented in a logical way.

You may want to record the data values, with units, in columns and identify the

quantity that is being measured at the top of each column.

5. If a mistake is made in recording a datum item, cancel the wrong value by drawing a

fine line through it and record the correct value legibly.

6. Get your data sheet, with your name, ID number and date printed on the right corner,

signed by the instructor before you leave the laboratory. This will be the only valid

proof that you actually did the experiment.

7. Each student, even though working in a group, will have his or her own data sheet

and submit his or her own written report, typed, for grading to the instructor by the

next scheduled lab session. No late reports will be accepted.

8. Actual data must be used in preparing the report. Use of fabricated, altered, and

other students’ data in your report will be considered as cheating. No credit will be

given for that particular lab and the matter will be reported to the Dean of Students.

9. Be honest and report your results truthfully. If there is an unreasonable discrepancy

from the expected results, give the best possible explanation.

10. If you must be absent, let your instructor know as soon as possible. A missed lab can

be made up only if a written valid excuse is brought to the attention of your instructor

within a week of the missed lab.

11. You should bring your calculator, a straight-edge scale and other accessories to class.

It might be advantageous to do some quick calculations on your data to make sure

that there are no gross errors.

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2.0 GENERAL LABORATORY RULES

ü  All Laboratory Students, Assistants, Faculty, and Staff must abide by the following safety rules when using the Physics Laboratory. This list may be modified as deemed appropriate for specific situations.

ü  Follow directions carefully when using any laboratory apparatus to prevent personal injury and damage to the apparatus.

ü  The instructions on all warning signs must be read and obeyed.

ü  Wear safety goggles for laboratory activities such as projectile motion, centripetal force, and other labs that involve rapid motion or acceleration of any kind. The goggles are provided by the department and each person in the lab must wear them.

ü   Long hair and loose items of jewelry or clothing MUST be secured during work with rotating machinery.

ü   Each student MUST know the use and location of all first aid and emergency equipment in the laboratories and storage areas.

ü   Each student must know the emergency telephone numbers to summon the fire fighters, police, emergency medical service or other emergency response services.

ü  Each student must be familiar with all elements of fire safety: alarm, evacuation and assembly, fire containment and suppression, rescue and facilities evaluation.

ü   NEVER aim or fire a projectile motion device at a person.

ü  Keep hands clear of any fan blades, moving parts, or projectile launchers (other than to pull the trigger).

ü  Laboratory walkways and exits must remain clear at all times.

ü  Glassware breakage and malfunctioning instrument or equipment should be reported to the Teaching Assistant or Laboratory Specialist. It is best to allow the Teaching Assistant or Laboratory Specialist to clean up any broken glass.

ü  All accidents and injuries MUST be reported to the Laboratory Specialist or Faculty teaching affected lab section. An Accident Report MUST be completed as soon as possible after the event by the Laboratory Specialist.

ü  No tools, supplies, or other equipment may be tossed from one person to another; carefully hand the item to the recipient.

ü  Casual visitors to the laboratory are to be discouraged and MUST have permission from the Teaching Assistant, Faculty Instructor of the section in question, or Laboratory Specialist to enter. All visitors and invited guests MUST adhere to all laboratory safety rules. Adherence is the responsibility of the person visited.

ü  No open-toed shoes are allowed in the laboratory (lab assistants and professor included), as weights or other objects may accidentally drop on people‘s feet; ordinary footware provides a measure of protection from such instances.

ü  Location of PPE (Personal Protection Equipment):

ü  Safety goggles are staged in the back in the drawer marked ―goggles

ü  A first aid kit is available near the sink at the front of the lab

ü  All Laboratory Students, Assistants, Faculty, and Staff must abide by the following safety rules when using the Physics Laboratory. This list may be modified as deemed appropriate for specific situations.

ü  Follow directions carefully when using any laboratory apparatus to prevent personal injury and damage to the apparatus.

ü  The instructions on all warning signs must be read and obeyed.

ü  Wear safety goggles for laboratory activities such as projectile motion, centripetal force, and other labs that involve rapid motion or acceleration of any kind. The goggles are provided by the department and each person in the lab must wear them.

ü  Long hair and loose items of jewelry or clothing MUST be secured during work with rotating machinery.

ü  Each student MUST know the use and location of all first aid and emergency equipment in the laboratories and storage areas.

ü  Each student must know the emergency telephone numbers to summon the fire fighters, police, emergency medical service or other emergency response services.

ü   Each student must be familiar with all elements of fire safety: alarm, evacuation and assembly, fire containment and suppression, rescue and facilities evaluation.

ü   NEVER aim or fire a projectile motion device at a person.

ü  Keep hands clear of any fan blades, moving parts, or projectile launchers (other than to pull the trigger).

ü   Laboratory walkways and exits must remain clear at all times.

ü   Glassware breakage and malfunctioning instrument or equipment should be reported to the Teaching Assistant or Laboratory Specialist. It is best to allow the Teaching Assistant or Laboratory Specialist to clean up any broken glass.

ü  All accidents and injuries MUST be reported to the Laboratory Specialist or Faculty teaching affected lab section. An Accident Report MUST be completed as soon as possible after the event by the Laboratory Specialist.

ü   No tools, supplies, or other equipment may be tossed from one person to another; carefully hand the item to the recipient.

ü  Casual visitors to the laboratory are to be discouraged and MUST have permission from the Teaching Assistant, Faculty Instructor of the section in question, or Laboratory Specialist to enter. All visitors and invited guests MUST adhere to all laboratory safety rules. Adherence is the responsibility of the person visited.

ü  No open-toed shoes are allowed in the laboratory (lab assistants and professor included), as weights or other objects may accidentally drop on people‘s feet; ordinary footware provides a measure of protection from such instances.

Location of PPE (Personal Protection Equipment) should be well known

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1.0 PHYSICS PRACTICAL S FOR O LEVEL.

PHYSICS PRACTICAL S

              O LEVEL

Introduction

Laboratories offer an ideal opportunity to learn and strengthen, by means of actual observations,

some of the principles and laws of physics that are taught to you in general physics

lectures. You will also become familiar with modern measuring equipment and learn the

fundamentals of preparing a report of the results.

THE OBJECTIVES OF PRACTICAL PHYSICS

"What are the objectives of laboratory work; why do

it?" Laboratory work may serve to:

Demonstrate the principles covered in your study material in physics;

ü  Provide familiarity with apparatus and enable them to handle the instruments and apparatus with purpose;

ü  Learn how to do science experiments;

ü  Develop an attitude of perfection in practical tasks.

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Common Physics Laboratory Apparatus and their uses

Physics Lab Equipment 

1. Ring & Ball Apparatus , 

It is used for demonstrating thermal expansion, comprising a captive brass ball secured to a mounted brass ring by a chain. Ring mounted on rod with a wooden handle. The ball passes through the ring when cold but will not pass through after being hot..

2. Rheostat Rheostats
are used as series resistors or potentiometers. Open slide wire type with a variety of resistance and current carrying capacity. Copper nickel alloys wire is oxidized to provide perfect insulation. It comes in various types of sizes, 6",8..

3. Resistance Box
Housed in box with brass knobs fitted. Provided with 4mm socket terminals. Accuracy +- 1% Range: 0.1 to 1, 1 to 10, 10 to 100, 100 to 1000, 1000 to 10000 OHMS. Also available till infinite range.

4. Vernier Calliper
Vernier Calliper, 12.5cm length. Available as Wheel Type & IME Type. Mostly chrome plated. Also available in S.S.

5. Aneroid Barometer-
Demo It is With 100mm dial graduated 28 to 31 inch of mercury and 960 to 1060 millibars. With plated blazel, cover glass and index plastic base approx 16cm dia. A very superior quality product for schools. Aneroid Barometer-Wall Type This Barometer is Hanging on Wall Type with front glass Diameter 10cm representing the rain, stormy weather, Dry & other conditions. It is Made as per Original ‘Sundo’s’ Technology of German. Ballistic Galvanometer Ballistic Galvanometer Battery

6. Eliminator Battery
Eliminator Bending of Beam Apparatus Bending of Beam Apparatus Compass Compass Compound Pendulum Compound Pendulum DANIEL CELL DANIEL CELL Comprising a heavy-gauge copper outer vessel with an internal perforated shelf for copper sulphate crystals, a porous pot and an amalgamated zinc rod fitted with a wooden supporting cap. The zinc rod and copper vessel are each provid.. DCC Wire DCC Wire Diesel Engine (Four Stroke) Diesel Engine comes in two types:Four StrokeTwo StrokeThe above product is nicely finished & export worthy quality. It isdemostration type with moving parts. Complete description is given onmodels key card. Diffraction Grating Transmission Type 30 x 25 mm. Available 15000 lines per inch. Plate covered with mounted in plastic frame.Diffraction Grating School quality 25 x 30 mm. 13400 lines per inch mounted in plastic frame. Transmission type 38 x 50 mm. Available 15,000 lin.. Digital Meter Digital Meter Dispensing Balance Dispensing Balance Dynamo Model Dynamo Model Eureka Wire Eureka Wire FORCE TABLE FORCE TABLE Fortin Barometer A superior pattern standard mercury barometer suitable for altitudes upto 600 meters. The barometer has a nominal bore of 7mm. Engine divided silvered scales covering 675 to 810mmHg. The reservoir has a standard type of adjustment screw and index.. Gas Taps Gas Taps G-Clamps G-Clamps Glass Slab Glass Slab Hydrometer Hydrometer Kater Pandulum Kater Pandulum Kitchen balance Kitchen balance Klinostat A clinostat is a device which is used to negate the effects of gravitational pull on plant growth. A single axis clinostat consists of a disc attached to a motor, originally clockwork but usually electric nowadays. The disc is held vertically and the.. Lee's Apparatus Rubber Gas tube apparatus for Lee's Method.For measuring thermal conductivity of poor conductors. Lens Double Concave Lens Double Concave Lens Set of 6 We customize the set of lens as per the customer requirement & also present it in a beautifully crafted velvet box as seen. Magnatic Needle With Stand Magnatic Needle With Stand Mariner Compass A compass with Aluminium bowl in gimbals and floating dial on Aluminium stand. Name originated from the usage of mariners for the direction. Meter Routine Voltmeter : moving iron, AC/Dc. Any single range: 0-1.5, 3, 5, 10, 25, 50, 100, 150, 250 and 300 Volts. Ammeter: Dual scale, moving coil for D.C. measurement. Any range 2.5/5, 1/5, 1.5/3, 5/10 Amps Meter Scale (Wooden) Meter Scale comes in two different qualities.NU-WOOD (Routine Quality)Teak Wood (Superior Quality) Micrometer Screw Gauge made of nickel plated brass, with ratched top, accurately machined S.S. rod. Range 0-25x0.01mm. Supplied in velvet /plastic case. Model Of Vernier Calliper This beautiful & technically crafted model of Vernier calliper is made of Plastic.Used for demostration in schools & also an export worthy product. Readily supplied in US & other countries.The demostration model of vernier calliper is alo.. Optical Bench (Double Rod) Optical Bench is readily used in school & colleges for performing optics experiment.Available in two different lengths : 1mtr & 1.5mtr longAvailable in three different materials: Iron, Brass & wooden.Provided with uprights, rod stand.. Pencil Jockey Pencil Jockey Petrol Engine (Four Stroke) Petrol Engine comes in two types: * Four Stroke * Two StrokeThe above product is nicely finished & export worthy quality. It is demostration type with moving parts. Complete description is given on models key c.. Potentiometer Potentiometer comes in two different ranges namely 4 wire & 10 wire. Research Optical Bench The bed is heavy cast iron with a strong control rib. Total Strength 180cm, Accuracy +/- 0.01%For detailed specification, kindly see the files uploaded in the product main image. Two different images are loaded & download it to get complete speci.. Resonance Apparatus Resonance Apparatus Rising Table Rising Table is an apparatus used for measuring the rise of fluid in capillary.It is used with in adjustment with reading telescope.Also known as capillary apparatus Slinky Spring Slinky Spring Slotted Weights Slotted Weights comes in different material & capacities.Material: Iron & BrassCapacity: 25, 50, 100, 250, 500 Gm, 2.5Kg especially for

7. sonometer. 
Sonometer Consists of wooden resonance box with two metal rules graduated into mm. Two wires of brass and steel attached to fixed bridge and tensioned by fine adjustment pegs , two movable bridges, pulley and fixed screw to enable a third wire to be fixed for .. Spectrometer Spectrometer Stop Clock Smith type, two sweep hands, one indicating seconds, the other recording minutes. Runs for 24 hours on one winding. Diameter of dial is 100mm divided 0-60 x1. Available in various qualities & ranges.

8. Tangent Galvanometer
Tangent galvanometer consists of Brass knobs & ring for more durability & results.It has metal tripod legs. Another version of the product is in R&D, which will provide die casted body with brass plugs & better outlook. Tapping Key Comprising a plated spring arm with press knob, a contact stud plated connecting strip and 4mm. socket terminals all mounted on a molded bakelite base

9. Triple Beam Balance
Triple Beam Balance, 750S; a single pan, low form balance. The balance has three notched weighing beams with centre indicating sliding masses, giving total weighing capacity of 610g. Additional supplementary masses are available to hang on the end of..

10. Young's Modulus Apparatus
Also known as Searl's Apparatus.To show the relationship between a load applied to a wire & the resulting extension. Comprising of engraved brass scale 10cm long & vernier reading 0.1 mm with tension weight but without masses.

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