Practical Physics I Pharmacy

DELTA UNIVERSITY FOR SCIENCE AND TECHNOLOGY FACULTY OF PHARMACY

Practical Physics I Fall 2012

PRACTICAL PHYSICS I[ ] Fall 2012

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Contents (1) Fine Measurement Apparatuses --------------------------------------------------------------------------- 2

(2) Determination of the Mechanical Equivalent of Heat (Joule's Law) by Electrical Method 12

(3) Determination of the Melting Point of a Solid Material ------------------------------------------ 15

(4) Determination of the Specific Gravity using Archimedes Principle and Density Bottle --- 18

(5) Speed of Sound in Air -------------------------------------------------------------------------------------- 29

(6) The Simple Pendulum ------------------------------------------------------------------------------------- 31

(7) Specific Heat by the Method of Mixing --------------------------------------------------------------- 33

(8) Measurement of Viscosity of a Liquid by Stokes Law ---------------------------------------------- 37



(1) Fine Measurement Apparatuses

0. Objective It is to measure the dimensions of a solid object using fine measuring

instruments like:

1. Vernier caliper,

2. Micrometer Screw Gauge and

3. Spherometer Screw.

1. Vernier caliper

1.1. Apparatus 1. Vernier caliper, and

2. Parallelepiped solid object.

1.2. Theory A very ingenious device for obtaining accuracy of a greater order than that

obtainable by eye-estimation was invented by (Pierre Vernier), and is

known by his name.

CRIZMA-PC&LAPTOPTypewritten Text

CRIZMA-PC&LAPTOPTypewritten Text



The vernier is a convenient attachment for determining accurately a

fraction of the finest division on the main scale of a measuring

instrument.

The simplest vernier scale has (10 divisions) that correspond in length to (9

divisions) on the main scale. Each vernier division is therefore shorter than

a main scale division by (101 ) of a main scale division. The first vernier

division is (101 ) main-scale division short of a mark on the main scale,

the second division is (102 ) short of the next mark on the main scale, and

so on until the tenth vernier division is (1010 ), or a whole division, short of a

mark on the main scale. It therefore, coincides with a mark on the main

scale.

If the vernier scale is moved to the right until one mark, say the third,

coincides with some mark of the main scale the number of tenths of a

main-scale division that the vernier scale is moved is the number of the

vernier division that coincides with any main-scale division. The third

vernier division coincides with a main-scale mark, therefore the vernier

scale has moved (3/10) of a main scale division to the right of its zero

position. The vernier scale thus tells the fraction of a main-scale division

that the zero of the vernier scale has moved beyond any main-scale mark.



The term "least count" is applied to the smallest value that can be read

directly from a vernier scale. It is equal to the difference between a main-

scale and a vernier division.

Least account nS

=

where (n) is the number of divisions on the vernier scale and (S) is the

length of the smallest main-scale division.

In order to make a measurement with the instrument, first determine its

least count, then read the number of divisions on the main scale before

the zero of the vernier scale and note which vernier division coincides with

a mark of the main scale. Multiply the number of the coinciding vernier

mark by the least count to obtain the fractional part of a main-scale

division to be added to the main-scale reading.

1.3. Method 1. Use the vernier caliper to measure the three dimensions of the

parallelepiped body, the length (L cm), the width (W cm) and the

depth (D cm).

2. Calculate the volume (V cm3) of the body.



1.4. Results The dimensions of the object:

Length (L) =

Width (W) =

Depth (D) =

Volume (V) = L * W * D = * * =



2. Micrometer Screw Gauge

2.1. Apparatus

1. Micrometer screw gauge, and

2. Spherical body.

2.2. Theory A micrometer screw gauge is a device for measuring very small distances.

It consists essentially of a carefully machined screw to which is attached a

circular scale.

Fig (4): The micrometer screw

In general, there is a circular head of a large diameter fitted to the screw

and moving past a scale fixed parallel to the axis. The head is subdivided

into a definite number of equal divisions, so that the screw can be turned

through fractions of a revolution and these fractions read on the

micrometer head.



In one complete revolution the point of the screw advances a distance

equal to the "pitch" of the screw, this being the distance between

similar points on consecutive turns of the thread.

The circular scale enables one to read the fractions of turns, and the

linear scale enables one to record the whole number of turns. The

least count of a micrometer screw is the pitch of the screw divided by

the number of divisions on the circular scale. One type of metric

micrometer has the linear scale graduated in mms, a screw having a pitch

of (1 mm), and (100 divisions) on the circular scale. The least count of this

instrument is ( mmmm 01.01001

= ).

Fig (5): The micrometer screw reading

2.3. Method

1. Use the micrometer to measure the radius (R cm) of the spherical

body.



2. Calculate the volume of the sphere (V cm3).

2.4. Results

The diameter of the sphere (D) =

The radius of the sphere (R = D/2) =

The volume of the sphere (V) = (4/3) R3 = 4/3*3.14*()3 =


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3. Spherometer Screw

3.1. Apparatus

1. Spherometer, and

2. Spherical peace.

3.2. Theory The spherometer is an instrument used for measuring the radius of

curvature of a spherical surface. In many cases as, for example when

dealing with a lens the surface is only a small portion of a sphere. In such

a case the radius of curvature is the radius of the sphere of which the

surface forms a part.

Fig (6): The Spherometer Fig (7): The measurement of lens

height

The instrument consists of a small table supported by three legs, placed

as nearly as possible at the corners of an equilateral triangle. Through the

centre of the table passes a screw of fine pitch forming a fourth leg. The



position of this leg can be read by means of a scale fixed at right angles

to the table and a circular scale attached to the head of the screw.

Measurement of the radius of curvature of a spherical surface

Place the spehrometer with the fixed feet resting on the surface,

and adjust the central foot till it just touches the surface. Read the circular

scale.

Replace the instrument on the plane surface and find how many whole

turns have to be made to bring the central foot back to the plane of the

other three feet. Using this reading with the readings of the circular

head in the two adjustments calculate the distance through which the

screw was moved.

Take the mean of several adjustments and let the height be (h cm).

Measure the distance between the two fixed feet carefully to (0.1 mm)

with a millimeter scale for each side of the triangle and take the mean

of the results: let it be (a cm). Then the radius of curvature is given by

the expression

26

2 hh

aR +=

(cm) (2)

3.3. Method

1. Put the spherometer on the spherical surface and adjust

its four legs and define the reading of the spherometer.

2. Put the spherometer on the plane surface and adjust

its four legs and define the reading to give the height

(h).

3. Calculate the radius of curvature (R) using Eq (2).



3.4. Results Reading of the spherometer on spherical surface (h1) =

Reading of the spherometer on plane surface (h2) =

The height of the spherical peace (h = h2 - h1) =

The triangle length (a) =

The radius of the spherical peace ( ) ( ) =+

=+=2626

22 hh

aR



(2) Determination of the Mechanical Equivalent of Heat (Joule's Law) by Electrical Method

0. Objective To determine the mechanical equivalent of heat (Joule's coefficient) by electrical method

1. Apparatus The experiment apparatus consists of:

1. Voltmeter and/or Ameter, (AC or DC)

2. Rheostat,

3. Power supply, (AC or DC)

4. Heating conductor,

5. Calorimeter within wooden box,

6. Thermometer, and

7. Stop watch

2. Theory If (V volt) is the potential difference developed due to the flow of current of intensity (I ampere) in a conductor of resistance (R Ohm), then the amount of electrical energy(E Joule) used in time (t sec) is given by:

E = V I t (Joules) (1)

If the conductor is immersed into a quantity of water of mass (mw gm) putted in a calorimeter of mass (mc gm) and specific heat (Sc cal gm-1 oC-1), the amount of energy of Eq (1) is changed into heat (H calorie) given by:



H = (mw + Wc) ( 2 - 1) (calorie) (2)

where [Wc = (mc Sc) cal oC-1] is the water equivalent of the calorimeter, ( 1 and 2 oC) are the initial and final temperatures of the system. The equation of equivalent between electrical (mechanical) energy and heat transformed is given by:

J (mw + Wc) ( 2 - 1) = V I t =RV 2 t, (Joule) (3)

where (J Joule Cal-1) is the mechanical equivalent of heat (Joule's coefficient) that is given by

= 2/( + )(2 1) ( 1)

Figure (1)

3. Method 1. Make the connections as shown in Fig (1). Adjust the value of the rheostat so that the potential (V) can be read accurately. Then switch off the transformer.

2. Find the mass of the calorimeter (mc), and water (mw) and note down the temperature of calorimeter and its contents (i)



3. Now switch on the transformer and start the stop watch. Keep on stirring the water, so that the temperature may be kept uniform.

4. Switch off the transformer when the rise in temperature becomes (5 oC or 6 oC). Note down the final temperature ( f). Also stop the stop watch and record the time for which the current was passed (t).

5. The readings of voltmeter (V) and ammeter (I) must be taken at an interval of (30 sec) [nearly constants]. The average values should be substituted in the formula.

4. Results The potential difference across the conductor (V) =

The current passes through the conductor (I) =

Mass of water taken (mw) =

Mass of calorimeter (mc) =

Specific heat of calorimeter (Sc) =

Water equivalent of calorimeter (Wc) = mc Sc = * =

Initial temperature of water (i) =

Final temperature of water (f) =

Time for which current was passed (t) =

The mechanical equivalent of heat (J) = 4.18 Joule/cal.

The resistance of the heater coil (R) = 2/(+)(21) =



(3) Determination of the Melting Point of a Solid Material 0. Objective To determine the melting point temperature of a solid material like wax.

1. Apparatus The apparatus consists of:

1. Beaker containing water,

2. Test tube fitted with a cork,

3. A thermometer passing through the cork,

4. Heating arrangement, and

5. Stop watch.

2. Theory A material often has a change in temperature when energy is transferred between it and its surroundings. There are some cases in which the transfer of energy does not result a change in temperature. This is the cases whenever the substance changes from one state to another; such as change from solid to liquid (melting) and from liquid to gas (boiling). This is called phase change. All such phase changes



involve a change in internal energy but no change in temperature. The amount of energy required during a phase change depends on the amount of the used substance.

The quantity of energy required for changing the phase of a unit of mass of a substance is called the Latent Heat (L cal gm-1).

The value of the Latent Heat for a substance depends on the nature of the phase change, as well as on the properties of the substance.

Latent heat of fusion (Lf cal gm-1) is the term used when the phase change is from solid to liquid (to fuse means to combine by melting).

3. Method 1. Take sufficient quantity of the solid material in a test tube and fix the cork along with the thermometer.

2. Adjust the test tube in a beaker containing water to do not contact the beaker body.

3. Heat water to its boiling point. The solid material in the test tube has melted and is in the liquid state.

4. Extinguish the heater and allow water and solid material to cool.

5. Record the temperature of the solid material each half a minute.

6. Plot a graph between time (t minutes) as abscissa and temperature ( oC) as ordinate.

7. The temperature corresponding to the horizontal line in the graph gives the melting point of the solid material (m oC). At this temperature, liquid material is converted into solid material without change of temperature, Fig (2). The temperature at the horizontal line in Fig (2) gives the melting.



4. Results (T min)

( ) (T min)

( ) (T min)

( ) (T min)

( )

Melting point of the used material (m) =


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(4) Determination of the Specific Gravity using Archimedes Principle and Density Bottle 0. Objective To determine the specific gravity of different liquids and solid materials using the density bottle and Archimedes principle

1. Apparatus 1. Sensitive balance,

2. Density bottle,

3. Set of weights,

4. Beaker,

5. Liquid, and

6. Heavy body and light body.

Theory The specific gravity (G) of a material is defined as the ratio between the weight (mass) (Mm gm) of a specific volume (V cm3) of this material to the weight (mass) (Mw gm) of the same volume of water at the same temperature. Also, the specific gravity (G) of a material can be defined as the ratio between the density of this material (m gm cm-3) and the density of the water (w gm cm-3) at the same temperature. Therefore;

= = = (1) where (g cm sec-2) is the acceleration of gravity.



(A) Archimedes Principle

1. Theory The upward force exerted by a fluid on any immersed object is called a buoyant force. The buoyant force is the resultant force due to all forces applied by the fluid surrounding the immersed object. Archimedes principle states that the magnitude of the buoyant force always equals the weight of the fluid displaced by the object. The buoyant force acts vertically upward through the point that was the center of gravity of the displaced fluid. Note that Archimedess principle does not refer to the makeup of the object experiencing the buoyant force. The objects composition is not a factor in the buoyant force because the buoyant force is exerted by the fluid. We can verify this as follows:

Fig (1): The buoyant force exerted by the fluid.

Suppose we focus our attention on the indicated cube of a solid material in the container illustrated in Fig (1.1). This cube is affected by two forces. One of these forces is the gravitational force (Fg dyne) that is acting down and is given by:

= = () (1)



where (Ms gm) is the mass of the solid material cube, (s gm cm-3) is the solid material density, (V cm3) is the cube volume and (g cm sec-2) is the acceleration of gravity. The other force is the buoyant force (FB Dyne) that is acting upward and it is due to the difference of the fluid pressure on the upper and lower faces of the solid cube.

The pressure at the bottom of the cube is greater than the pressure at the top by:

= where (f gm cm-3) is the density of the fluid, and (h cm) is the height of the cube. The pressure difference (P Dyne cm-2) between the bottom and top faces of the cube is equal to the buoyant force per unit area of those faces that is:

=

( 2) where (A cm2) is the area of the upper or lower faces of the cube. Therefore, the buoyant force is given by:

FB = P A = f g h A = f V g, (Dyne)

where (V cm3) is the volume of the cube.

Because the mass of the fluid in the cube is (Mf = f V) we see that

FB = Mf g = f V g (Dyne) (2)

Thus, the buoyant force is a result of the pressure differential on a submerged or partly submerged object.

Using Eqs (1) and (2), the net force (F dyne) acts on the body immersed in the fluid is given by:

F = Fg FB = (Ms - Mf) g = (s - f) V g (Dyne) (3)

This force (F dyne) equals the weight of the body totally immersed in the fluid (Wsf dyne) while the gravitational force (Fg dyne) is the weight of the body in air (Ws dyne). Therefore, we have for submerged body in the fluid the following:



1. If the gravitational force (Fg dyne) is greater than the buoyant force (FB dyne), the body will be totally submerged in the fluid.

2. If the gravitational force (Fg dyne) is equal to the buoyant force (FB dyne), the body will be partially submerged in the fluid.

The specific gravity of the body (GS), defined in Eq (1), and using Eqs (1) and (3) is given by:

= = = = (4) where (FBw dyne) is the buoyant force of the water on the solid body, (FBL dyne) is the buoyant force of the liquid on the solid body, (Ws dyne) is the weight of the solid body in air, (WsL dyne) is the weight of the solid body totally immersed in the liquid and (GL) is the specific gravity of the used liquid. The specific gravity of a fluid (liquid) (GL) can be given, using this method, as:

= = = = (5) where (Wsw dyne) is the weight of the solid body totally immersed in the water.

2 Method 2.1. Verification of Archimedes Principle

1. Measure the dimensions of regular shape solid body using Vernier and micrometer and calculate its volume (V).

2. Weight this body in air using a balance (Ws).

3. Put a beaker filled with a liquid of known density (L) on a bridge on the base of the balance does not touch the balance pan.

4. Calculate the weight of the replaced liquid (WL = V L).

5. Hang the solid body in the balance cope to be totally immersed in the liquid in the beaker and measure the weight (WsL).

6. Calculate the liquid buoyant force (FB =Ws WsL).



7. Repeat the steps (1-6) for different regular shape solid bodies and different liquids with known densities.

8. Note that the results verify Archimedes's principle (FB = WL).

2.2. Determination of the Specific Gravity of a liquid

1. Use a solid body that does not solved with the used liquid and the water and the body totally submerged in both of them.

2. Using a balance, measure the weight of the solid body in air (Ws).

3. Put a beaker filled with this liquid on a bridge on the base of the balance does not touch the pan.

4. Hang the body with weightless wire in the cope of the balance totally immersed in the liquid and does not touch the walls or the base of the beaker. Measure the weight of the solid body immersed in the liquid (WsL).

5. Repeat steps (3 and 4) for a beaker filled with water and measure the weight of the solid body totally immersed in the water (Wsw).

6. Using Eq (5) calculate the specific gravity of the liquid

= 2.3. Determination of the Specific Gravity of a solid body

1. Using a balance, measure the weight of the solid body in air (Ws).

2. Use a liquid with known density (L) that does not solve the solid body material and the body totally submerged in it.


4. Hang the body with weightless wire in the cope of the balance totally immersed in the liquid and does not touch the walls or the



base of the beaker. Measure the weight of the solid body immersed in the liquid (WsL).

5. Using Eq (4), the specific gravity of the solid body =

is calculated, where = and (w) is the water

density at the same temperature of the experiment.

2.4. Determination of the Specific Gravity of a solid floating on water

1. Using a balance, measure the weight of the floating solid body in air (Ws).

2. Use a liquid with known density (L) that does not solve the floating solid body material and the body totally submerged in it.

3. Use a solid body that is totally immersed in the used liquid and dissolved in it.


5. Hang the immersing body with weightless wire in the cope of the balance totally immersed in the liquid and does not touch the walls or the base of the beaker. Measure the weight of the immersing body immersed in the liquid (WsL1).

6. Tie the floating solid body with the immersing body and measure the weight of both immersed totally in the liquid as in step (5) to be (WsL2).

7. Calculate the weight of the floating solid body immersed in the liquid as (WsL = WsL2 WsL1).

8. Using Eq (4), the specific gravity of the solid body =

is calculated, where = and (w) is the water

density at the same temperature of the experiment.



3. Results 3.1. Verification of Archimedes's Principle

The volume of the solid body (V) = * * =

The weight of the body in air (Ws) =

The used liquid density (L) =

The weight of the replaced liquid (WL = V L) =

The weight of the solid body totally immersed in the liquid (WsL) =

The liquid buoyant force (FB =Ws WsL) = - =

Note that the results verify Archimedes's principle (FB = WL)

3.2. Determination of the Specific Gravity of a liquid

The weight of the solid body in air (Ws) =

The weight of the solid body immersed in the liquid (WsL) =

The weight of the solid body totally immersed in the water (Wsw) =

The specific gravity of the liquid = =

3.3. Determination of the Specific Gravity of a solid body

The weight of the solid body in air (Ws) =

The density of the used liquid (L) =

The weight of the solid body immersed in the liquid (WsL) =

The specific gravity of the used liquid (GL) =

The specific gravity of the solid =



3.4. Determination of the Specific Gravity of a solid floating on water

The weight of the floating solid body in air (Ws) =

The density of the used liquid (L) =

The weight of the immersing body immersed in the liquid (WsL1) =

The weight of both immersed totally in the liquid (WsL2) =

The weight of the floating solid body immersed in the liquid (WsL = WsL2 WsL1) = - =

The specific gravity of the used liquid (GL) =

The specific gravity of the solid =



(B) Determination of Specific Gravity using Density Bottle

1. Theory If the empty, drayed density bottle is weighted to have mass (M gm) then it is fully filled with water and the mass of the water is measured to be (Mw = M1 - M gm) and the bottle is again fully filled with the required liquid and the mass of this liquid is measured to be (ML = M2 - M gm), the gravity density of the liquid (GL), using Eq (1), is given by:

= / = (1) To determine the gravity density of a solid powder (GS) using the density bottle we must use a liquid which does not solve this solid powder. [If the water does not solve the required solid powder, we can use the water directly.] As the specific gravity of the solid powder, using Eq (1), is given by:

= / = /1/ 1// = 11 1 = (2) where (Ms gm) is the mass of a quantity of solid powder of volume (V or V1 cm3), (Mw gm) is the mass of a quantity of water of volume (V cm3), (ML1 gm) is the mass of a quantity of the used liquid of volume (V1 cm3) and (GL) is the specific gravity of the used liquid.

2. Method 1. Measure the mass of the empty, drayed density bottle with its cover (M).

2. Fully fill the density bottle with water, put its cover slowly and dray it from outside. Measure the mass of the bottle fully filled with water (M1).

3. Calculate the mass of the water fully filled the bottle (Mw) = M1 M.

4. Empty the bottle from water and dray it from inside and outside.



5. Fully fill the density bottle with the liquid, put its cover slowly and dray it from outside. Measure the mass of the bottle fully filled with the liquid (M2).

6. Calculate the mass of the liquid fully filled the bottle (M) = ML2 M.

7. Empty the bottle from the liquid and dray it from inside and outside.

8. Calculate the specific gravity of the liquid (GL)

9. Put a quantity of the solid powder in the density bottle (about its third) and measure the mass of the bottle with its cover and the quantity of solid powder (M3).

10. Calculate the mass of the solid powder inside the bottle (Ms) = M3 M.

11. Complete the bottle with the used liquid to be fully filled and put the cover slowly. Dray the bottle from outside. Measure the mass of the bottle with its cover, the solid powder and the liquid (M4).

12. Calculate the mass of the liquid that completed the bottle (M5) = M4 M3.

13. Calculate the mass of the liquid that has the same volume of the solid powder (ML1) = M ML5.

14. Calculate the specific gravity of the solid powder material and the specific gravity of the used liquid (GL). [If the water is used as the liquid in this part, the specific gravity of the water = 1]

3. Results

The mass of the empty, drayed density bottle with its cover (M) =

The mass of the bottle with its cover fully filled with water (M1) =

The mass of the water fully filled the bottle (M) = Mw1 M =



The mass of the bottle with its cover fully filled with liquid (M2) =

The mass of the liquid fully filled the bottle (M) = ML2 M = The

specific density of the liquid = The mass of the bottle with its cover with some of solid powder (M3) =

The mass of the solid powder putted in the bottle (Ms) = M3 M =



(5) Speed of Sound in Air Theory:

- Sound is a longitudinal wave consists of compressions and relaxations.

- If there's a reflecting surface (like water), the waves reflects on themselves forming standing waves.

- Standing waves consists of nodes and anti-node. - For air columns closed from one of its ends, the length of the

tube at resonance when the tube is making the primary note is L = / 4 = 4L

- Since speed of sound is given by V =

- Then, V = 4L 1

4

=VL

- Since the anti-node is formed above the air column by a distance = 0.6R, where is the inner radius of the tube.

- Then RVL 6.014

=

- So the relation between L and (1/) is a straight line which intersects L-Axis at -0.6R and has slope = V/4

Apparatus: Tuning Forks with different frequencies, resonance tube, water-filled Beaker and a rubber Pad.

Method: 1. Arrange the forks from the higher to the lower frequencies. 2. Strike the first fork (512 Hz) on the rubber pad and put it near

the resonance tube.



3. Move the tube up slowly until you get the first resonance. Then record the length of the tube from the water surface to the end of the tube. (L1)

4. For the same fork obtain the resonance three times and record the three lengths (L1, L2, L3) and calculate their average. (L).

5. Repeat steps [2] to [4] for different frequencies. 6. Plot a relation between (1/) and (L) which ) is a straight line

which intersects L-Axis at -0.6R and has slope = V/4 7. From the slope calculate V = 4 Slope

Results:

1/ Measured Lengths Average Length (L) L1 L2 L3

0.6 R = ------- R = -------------------- Cm

V = 4 Slope = ----------------- Cm/Sec

Vo = ---------------------------------- Cm/Sec

%100=Vo

VoVError = -----------------------------------



(6) The Simple Pendulum Apparatus

Simple pendulum , Meter rule, and Stop watch.

Theory For the simple pendulum , if it left to oscillate it will give a simple harmonic motion, this motion can be described by the newton's second law .

F = M 2

2

dtxd

(1)

The periodic time of this motion given by

T = 2gL

. (2)

T2 = g

4 2L, (3)

Relation between T2 and L is a straight line

Slope = g

4 2, (4)

that can be used to calculate the acceleration of gravity (g).

Method 1. take a certain length L , Displace the pendulum a small angle () from the

vertical and release it to oscillate. 2. Measure the time (t sec) for (10) complete periods of motion, then calculate the

periodic time (T = t/10 sec). 3. Repeat the above steps for different pendulum lengths. 4. Plot a graph between (L cm) and (T2 sec2) as shown Fig . 5. Calculate the slope of the resultant straight line, which will be used to calculate

the acceleration of gravity (g).



5. Results The number of complete oscillations =

L (cm) T10 (sec) T (sec) T2 (sec2)

The slope of the straight line = sec2.cm-1,

The acceleration of gravity (g) = slope4 2

=



(7) Specific Heat by the Method of Mixing Objective To calculate the specific heat of a liquid or solid substance using the

mixing method

Apparatus The apparatus of the experiment consists of:

1. Solid material (lead shots or sands or copper chips) and liquid material,

2. A calorimeter with stirrer, 3. Heat insulating box, 4. Two Celsius thermometers, 5. Heater, and 6. A boiler.

Fig (1): Specific heat using mixing method



2. Theory The quantity of heat that is required to raise the temperature of the

whole quantity of the material by one degree is known as the heat

capacity of the material. But the specific heat of a material is defined as

the quantity of heat required to raise the temperature of one gram of

the material one temperature degree. The specific heat of a material

(solid or liquid) can be measured experimentally as follows. Suppose (ms

gm) grams of a solid material of specific heat (Ss cal gm-1 0C-1) at

temperature (Os C) is added to (mw gm) of water at temperature (O C)

in a calorimeter whose water equivalent is (Wc = mcSc cal 0C-1). The final

temperature reached is (Of oC). Applying the principle that:

Heat gained = Heat lost. (1)

Heat gained by water and calorimeter =

(mw + Wc) (Of - O), (cal.)

(2)

Heat lost by the solid = ms Ss (s f), (cal) (3)

(mw + Wc) (f i) = ms Ss (s f) (4)

Ss = ( + )( )

( ) (cal. gm-1. oC-1) (5) N. B.: Used units are cgs units, so the specific heat of water = 1 cal. gm-1. oC-1

3. Method

1. Take two Celsius thermometers. See that both show the same temperature when immersed in water.

2. Take a boiler and place it on a heater. Start heating the boiler with the heater. Put some quantity of the solid into the tube of the boiler

and fix the thermometer so that the bulb is inside the solid. The

bulb should not break. Adjust carefully.



3. Take the calorimeter with the stirrer and find its mass (mc).

4. Put water at room temperature in the calorimeter approximately to third of its volume. Find the whole mass (m1).

5. Record the temperature of water and calorimeter (0).

6. When the thermometer in the tube of the boiler shows constant temperature, read the temperature, which is that of the hot solid

0).

7. Transfer the hot solid into the calorimeter immediately and stir the contents.

8. When the thermometer shows constant temperature for nearly a minute, read the final temperature (0)

9. Remove the thermometer and notice that no water drop sticks to the thermometer.

10. Weigh the calorimeter and its contents. Find the whole mass (m2).

Precautions

1. The calorimeter should be kept in the wooden box except when it is weighed.

2. The hot solid should be quickly transferred into the calorimeter. 3. The final temperature should be recorded just after stirring the water.

4. Temperature should be correctly recorded.



5. The calorimeter should be covered with a lid when water in the calorimeter is stirred.

1. Determination of the Specific Heat of a Solid

4.1. Results Mass of calorimeter + stirrer (mc) =

Specific heat of calorimeter (from constants' tables) (Sc) =

Mass of calorimeter + stirrer + cold water (m1) =

Temperature of cold water and calorimeter (00) =

Temperature of hot solid 0) =

Final temperature (0) =

Mass of calorimeter + stirrer + cold water + solid (m2) =

Mass of cold water (mw) = mj - mc =

Mass of solid (ms) = m2 - mj =

Water equivalent of calorimeter (Wc) = mc Sc = *

Specific heat of solid (Ss) = ( + )( )

( ) = ( + )( ) ( ) = Specific heat of the solid (form constant tables) (S0) =

Error % = ( 0) 0 100 % = ( ) 100 % =



(8) Measurement of Viscosity of a Liquid by Stokes Law

Objective To determine the viscosity of a liquid using the Stokes law

Apparatus 1. Measuring cylinder (a long glass tube),

2. The liquid,

3. Stop-watch,

4. Small steel ball-bearings of varying diameter,

5. Micrometer, and

6. Meter rule.

2. Theory The term viscosity is commonly used in the description of fluid flow to

characterize the degree of internal friction in the fluid. This internal

friction, or viscous force, is associated with the resistance that two

adjacent layers of fluid have to moving relative to each other. The

coefficient of viscosity (n) is defined as the ratio of the shearing

stress to the rate of change of the shear strain.

According to Stokes law a small spherical ball of radius (r cm) falling

through a fluid of viscosity coefficient ( Dyne sec cm-2) acquires a

terminal velocity (v0 cm sec-1) and affected with a viscous force given by

Fv = 6v0 r. (Dyne)



(1)

In the steady state, when the spherical ball falls with constant velocity,

the viscosity force (Fv dyne) is equal to the downward force Fd = 4 3 r3 (s - L )g (Dyne) (2) where (g cm sec-2) is the acceleration of gravity, (s gm cm-3) is the density

of the balls material and (L gm cm-3) is the density of the liquid.

Therefore, the viscosity coefficient is given by

= 2 20 (s L )g (gm.cm-1.sec-1= Poise) (3) This relation is applied only for terminal velocity (v0 cm sec-

1) of a spherical ball falling through an infinite extent of

liquid. For a spherical ball of radius (r cm) falls axially in a

viscous fluid in a cylindrical tube of radius (R cm), there is a

correction due to wall effects of the tube. This correction is

given by Landenberg as

0 = (1 + ) (cm. sec-1) (4) where (k) is a constant, (v cm sec-1) is the observed terminal velocity,

and (v0 cm sec-1) is the true terminal velocity for an infinite extent of

the fluid.



3. Method

1. Measure the radius of the measuring cylinder (long tube) (R).

2. Fill the measuring cylinder with the liquid,

3. Fix two marks (X) and (Y) near the top and the bottom of the tube.

4. Measure the distance between the two marks (X) and (Y), (L).

5. Measure the radius of the largest ball-bearing (r) using the

micrometer.

6. Drop in the ball-bearing and measure the time (t) of falling

of the ball between the two marks (X) and (Y).

7. Calculate the average velocity of dropping the ball (v =

L/t). Then, calculate the corrected velocity (v0).



8. Repeat the steps (4-7) for different ball-bearings.

9. Plot the relation between the ball square radius (r2) as abscissa and

the corrected velocity (v0) as ordinate

4. Results

The temperature of the liquid () =

The radius of the measuring

cylinder (long tube) (R) = The

distance XY (L) =

Zero error of micrometer gauge =

The density of the liquid (L) =

The density of the ball-bearings material (s) =

r ( ) r2 ( ) t ( ) v (L/t) ( ) v0 ( )

Slope (v02

) = The viscosity coefficient () =

2 1 s L g = 2 1 ( ) 981 =



The viscosity coefficient at temperature ( 0C) from tables (0) =

Error % = 0 0 100 % = 100 % = %

Notes:

1. Fix the first mark (X) below the top of the liquid with

sufficient distance, so the ball-bearing reaches a steady

velocity by the time it reaches (X). Fix the second mark (Y)

with sufficient distance from the bottom of the cylinder.

2. Measure the diameter of each ball-bearing in two

perpendicular directions using the micrometer.

3. Note the zero error of the micrometer.

4. Measure the density of the liquid (L) and its temperature ().

(1) Fine Measurement Apparatuses0. Objective1.1. Apparatus1.2. Theory1.3. Method1.4. Results2. Micrometer Screw Gauge2.1. Apparatus2.2. Theory2.3. Method2.4. Results3. Spherometer Screw3.1. Apparatus3.2. Theory3.3. Method3.4. Results

(2) Determination of the Mechanical Equivalent of Heat (Joule's Law) by Electrical Method0. Objective1. Apparatus2. Theory3. Method4. Results

(3) Determination of the Melting Point of a Solid Material0. Objective1. Apparatus2. Theory3. Method4. Results

(4) Determination of the Specific Gravity using Archimedes Principle and Density Bottle0. Objective1. ApparatusTheory1. Theory2 Method3. Results1. Theory2. Method

(5) Speed of Sound in AirTheory:Apparatus:Method:Results:

(6) The Simple PendulumApparatusTheoryMethod5. Results

(7) Specific Heat by the Method of MixingObjectiveApparatus2. Theory3. Method1. Determination of the Specific Heat of a Solid4.1. Results

(8) Measurement of Viscosity of a Liquid by Stokes LawObjectiveApparatus2. Theory3. Method4. Results

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Practical Physics I Pharmacy