Tuesday, November 30, 2010

Carbon-14 dating and Uranium Lead Dating

Please click on the following link to refer the notes provided :

http://lfcsphysicsnotes.blogspot.com/

Sunday, November 7, 2010

EXPERIMENT – 10

AIM:


To determine the focal length of a convex lens using a vertical pin and a plane mirror by parallax removal method.


APPARATUS: 

Convex lens, plane mirror, vertical pin, stand for mounting and a scale.

THEORY:

If an object is kept at the focus of a convex lens, the light rays incident from the object on the lens become parallel to the principal axis after refraction. The refracted rays fall normally on the plane mirror and retrace their path to form an image on the object itself.
PROCEDURE:

1. Mount the pin, convex lens and the plane mirror on their respective stands as shown in the figure.
2. Adjust the height of the pin such that the tip of the pin and the optical centre of the lens are at the same horizontal level.
3. Adjust the position of the needle so that on looking through the lens at the image of the needle, there is no parallex between the object and the image.
4. Note the values of x1 and x2 from the scale.
5. Repeat the experiment for different positions of the convex lens.

PRECAUTIONS:

1.The tip of the pin and the optical centre of the lens should be at the same horizontal level.
2.The parallax should be properly removed.


RESULT:

The focal length of the lens is found to be --------

Tuesday, November 2, 2010

EXPERIMENT – 9

AIM:

To find the effort required to roll a roller up an inclined plane and to determine its MA and VR for different angles of inclination.

APPARATUS: 

An inclined plane, roller,weight box, pan, protractor and spring balance.

THEORY:

An inclined plane is a simple machine whose
 MA = Load/ Effort = L/E and 
VR= l/h where l= length of inclined plane and h= height of inclined plane.

PROCEDURE:
1. Fix the angle of inclination \theta  of the inclined plane and note the values of l and h.
2. Note the weight of the roller with the help a spring balance and let it be L.
3. Tie the end of the string with the hook of the roller and pass it over the pulley. Tie the other end to the pan.
4. Note the weight of the empty pan. Let it be 'w'.
5. Add weights to the pan gradually till the roller just begins to slide. Let the total weights be  'W'. Hence the effort required is 'W+w'.
6. Repeat the experiment for different angles of inclination.
7. Calculate the MA and VR for each set.

PRECAUTIONS:

1. Clean and polish the surface of the inclined plane to minimise the friction.
2. Pulley should be oiled.
3. Pan should not touch the table or the inclined plane.
4. Increase the weight of the pan gradually.
5. The inclined plane should be knocked gently each time.

RESULT:

It is found that for each angle of inclination, MA < VR as the friction between the roller and the inclined plane increases the effort required.

Tuesday, June 22, 2010

EXPERIMENT – 8


AIM:

To verify the Ohm's law and hence find the value of the unknown resistance.

APPARATUS:

Battery, Ohm's law apparatus which comprises of ammeter, voltmeter, resistance wire, switsh and connecting wires.

PRINCIPLE:

According to the Ohm's law, at a constant temperature, the current flowing through a conductor is directly proportional to the potential difference applied across the ends of the conductor.

FORMULA:

V = IR
Where :
V=Potential difference across the ends of the conductor
I =Current flowing through the conductor
R = Resistance of the conductor

PROCEDURE:

1.Set up the apparatus as shown in the figure.
2.For various positions of the rheostat take the ammeter and voltmeter readings.
3.Take five sets of observations.
4.Take the mean of all the observations.
5.Draw a graph with voltage along the x axis and current along the y axis.

PRECAUTIONS:

1.The connections should be tight.
2.The ends of the wires must be cleaned with sand paper before making the connections.
3.The current should not be allowed to pass through the circuit for a very long time as it heats up the wire and changes its resistance.

RESULT:

1.The graph between current and potential difference is found to be a straight line.
2.The value of the unknown resistance is found to be _________ 

Tuesday, June 8, 2010

EXPERIMENT – 7

AIM:

To find the centre of gravity of lamina cut in various shapes.

APPARATUS:

Lamina cut in various shapes (square, rectangle, circle, scalene triangle, irregular shape), nail and plumb-line.

PRINCIPLE:

The Center of Gravity of an object is that point where the entire weight of the object is supposed to act.

PROCEDURE:

Make 3 small holes near the edge of the first lamina.
Fix a nail on the soft-board.
Suspend the lamina from any hole such that it is free to oscillate.
Now suspend the plumbline from the nail, and when the plumbline is stationery draw a line on the lamina along the string of the plumb-line.
Repeat the experiment with the other holes to get 3 lines on the lamina.
The point of intersection of the 3 lines is the center of gravity.
Repeat the above steps for other shapes of lamina.

PRECAUTIONS:

Holes should be small so that not too much of the lamina is removed.
The lamina when suspend at a given point should be able to swing freely at that point.

RESULT:

The center of gravity of various shapes is found as shown in the figures.

NOTE FOR STUDENTS : THIS EXPERIMENT REQUIRES TWO PAGES. HENCE LEAVE AN EXTRA PAGE IF YOUR EXPERIMENT IS COMPLETED IN 1 PAGE.

EXPERIMENT – 6

AIM:
To find the weight of an unknown object using the principle of moments.

APPARATUS:
Metre scale, retort stand, known weight, unknown weight and a thread for hanging.

PRINCIPLE:

When a body is in equilibrium under the action of a number of forces, then the algebraic sum of moments about any point is zero under the condition of equilibrium. Under this condition :

Load x Load Arm = Effort x Effort Arm

FORMULA:

Ax = By
Where :
A= known weight
b= unknown weight
x= distance of known weight from the fulcrum
y= distance of unknown weight from the fulcrum

PROCEDURE:

1.Hang the metre rod using thread from the stand at the point of the centre of gravity of the metre scale.
2.Suspend the known weight on the left hand side of the fulcrum at distance of x cm from the centre of gravity
3.Suspend the unknown on the right hand side of the fulcrumand balance the scale.
4.Note the distances x and y
5.Calculate the unknown weight

PRECAUTIONS:

1.The experiment should be done away from fans, open windows etc to aviod disturbance due to air currents.
2.The distances x and y from the fulcrum should be carefully noted..
3.The loops of the thread must be parallel to the metre scale markings.

RESULT:

The weight of the unknown object is found to be ________ gf.

EXPERIMENT – 5

AIM:

To draw the lines of force around a bar magnet placed in the magnetic maredian with its north pole facing the geographical north and to obtain the null points.

APPARATUS:

Drawing board, paper, cello tape magnetic compass needle and a bar magnet.

THEORY:

A bar magnet creates a magnetic field around itself and at the same time the earth also has a uniform magnetic field at a given location. When the combined magnetic field is plotted around the bar magnet, then there are certain points where the magnetic field due to the bar magnet is equal and opposite to the magnetic field due to the earth. These points are called null points.

PROCEDURE:

1.Fix a sheet of paper on the drawing board with cello tape.
2. Draw a line in the middle of the paper and put a compass needle on the line.
3. Rotate the drawing board such that the direction of the compass needle coincides with the direction of the line drawn. Remove the compass needle.
4. Put the bar magnet on the paper such that its long edge touches the line and the north pole of the magnet points towards the geographic north. Mark the outline of the magnet and the drawing board to make sure that both are not disturbed during the experiment.
5. Put the compass needle near the north pole of the bar magnet and mark dots at the ends of the needle with a pencil.
6. Pick the compass needle and place it in such a manner that the south end is kept at the point where the north end was earlier located. Go on repating this process till you reach the other end of the magnet. In this way a line of force has been located.
7. Starting from different points near the north pole of the bar magnet, several such lines are drawn.
8. At the location of neutral points the compass needle does not experience any force.

PRECAUTIONS:

1. The position of the magnet and the drawing board should not be disturbed during the entire experiment.
2. No magnet or magnetic substance should be kept near the board.
3. The magnetic needle should be kept exactly on the dot previously obtained.

RESULT:

The magnetic field and the null points are as shown in the figure.

EXPERIMENT – 4

AIM:

To determine the focal length of the given convex lens by using a candle and a screen and to calculate the power of a lens.

APPARATUS:

A convex lens, candle, scale, match box and a screen.

FORMULAE :



(Students are requested to leave four lines here)



Where:
f = focal length
P = power of the lens in dioptres
u = object distance
v = image distance

PROCEDURE :

1. Set up the experiment as shown.
2. Determine the approximate focal length by focusing a distant object like a tree on the opposite wall. Let its value be f.
3.Mark points at a distance f and 2f on one side of the lens.
4. A candle is kept beyond 2f on this side.
5. A screen is kept on the other side and its position is adjusted to obtain a sharp, inverted and a diminished image on the screen.
6. The values of u and v are noted
7. The candle is shifted to a new position and the screen is once again adjusted to record the new values of u and v.
8. Six such observations are taken and the focal length is calculated for all these observations.
9. The mean value of f is calculated.

PRECAUTIONS:

1. The object, lens and the screen should should be held vertical.
2. The objects likely to catch fire must be kept away from the candle flame.

RESULT:

The focal length of the lens is found to be ____ cm and the power of the lens is calculated as _____ dioptres. The power is positive as the lens is a convex lens.

Sunday, June 6, 2010

EXPERIMENT - 3

AIM:
To determine the angle of minimum deviation of a prism using a deviation graph.

APPARATUS:
Glass prism, drawing board, drawing pins, sheets of paper, cello tape, protractor and a pencil.

PRINCIPLE:
On increasing the value of the angle of incidence i, the angle of deviation ẟ first decreases to a minimum value and then increases.


PROCEDURE:

1. Fix a sheet of paper on the drawing board with cello tape.
2. Place the glass prism and draw its boundary ABC.
3. Remove the prism from its place..
4. Mark a point O as shown in the figure and draw the normal NON’ through O.
5. Draw a line XO such that the angle of incidence XON is 40 degrees.
6. Place the glass prism back to its original position.
7. Fix two pins along the line XO.
8. Looking through the other side AC of the prism, fix two more pins such that these two pins and the images of the previous two pins seem to be in a straight line.
9. Remove the pins and the prism and draw the refracted and the emergent rays OY and YZ.
10. Produce the incident ray forward and the emergant ray backward to get the angle of deviation ẟ.
11. Take four more observations with different values of angles of incidence each time.
12. Plot a graph between angle of incidence on the x- axis and the angle of deviation on the y – axis.
13. Determine the angle of minimum deviation from the graph.

PRECAUTIONS:

1. The prism must be correctly placed on the out line for all the observations.
2. Pins must be vertical.
3. While viewing through the other end of the prism, the feet of the pins must be adjusted to form a straight line and not the heads.


RESULT:
The angle of minimum deviation is found to be ____