Demonstrations

Paper Chromatography

AIM: To separate the pigments from fresh leaves using paper chromatography.

MATERIALS REQUIRED: Acetone, leaves, mortar and pestle, pencil, capillary tube, spatula.

PROCEDURE: Take a few freshly plucked green spinach leaves.
·         Using scissors, cut the spinach leaves into small pieces and let them fall into the mortar.
·         Take a measuring cylinder that contains 5ml of acetone and pour it into the mortar.
·         Grind the spinach leaves using the mortar and pestle.
·         Place the extract into a watch glass using a spatula.
·         Take a strip of filter paper having a narrow notch at one end of the strip.
·         Take a pencil and a scale and draw a horizontal line with a pencil about 2-3 cm away from the tip of the notch.
·         Put a drop of the pigment extract in the middle of the line with the help of a capillary tube.
·         Allow the drop to dry and repeat till four or five drops are placed on the paper.
·         Take the chromatographic chamber and pour ether acetone solvent in it.
·         Fold one end of the filter paper strip and staple it.
·         Using a thread, hang the filter paper strip in the chromatographic chamber.
·         The loading spot should remain about 1 cm above the solvent level.
·         Leave the chromatographic chamber undisturbed for some time.
·         We can observe, as the solvent moves through the paper, it spreads the different pigments of the mixture to various distances.
·         When the solvent rises about 3/4th up the strip, remove the strip carefully and let it dry.

OBSERVATION:-The dried chromatographic paper strip shows four distinct paper bands. Different pigments can be identified   by their colours.

RESULT:- The topmost orange yellow band of pigments in the separation corresponds to carotene. The yellowish band appearing below it indicates the xanthophylls. The third from above dark green band represents chlorophyll a. The lowermost yellowish green band is that of chlorophyll b.

MINI TESLA COIL

Aim:- To construct a mini tesla coil

Apparatus:- Copper wire, PVC pipe, on/off switch, 2N2222A Transistor, 22Kohm resistor, 9v battery and clip.

Circuit Diagram:-

                                                 
Working Principle:-
·       FARADAY’S LAW OF MAGNETIC INDUCTION:-“The induced electromotive force in any closed circuit is equal to the negative of the time rate of change of the magnetic flux enclosed by the circuit.” According to which, when a conductor is placed under a varying magnetic field, a small current will be induced inside the conductor. For a Tesla coil this conductor will be called as the secondary coil and the varying magnetic field will be produced by the primary coil by passing an oscillating current through the primary coil.

·       MAGNETIC FLUX:- Magnetic flux is the number of magnetic field lines passing through a closed surface (such as a conducting coil). 
Observation:- when the circuit is turned on and when we take the tube at the vicinity of the coil, the tube glows without any electric supply.

Observation:- when the circuit is turned on and when we take the tube at the vicinity of the coil, the tube glows without any electric supply.