Practical Two and Three (Hot Stuffs and Types of Flames)

So in Practical two, we learnt how to use the Bunsen Burner. Now, lets review the parts of a Bunsen Burner- It has a Barrel, Air Hole, Jet, Collar and the Gas Tap. The Barrel is to raise the flame to a suitable height for burning, the collar, to control the amount of air entering the burner by opening or closing the air-holes, the gas tap to control the flow of gas to the Bunsen Burner, the Air Hole to allow air to enter the burner, the Jet to enable the gas to rush out from the gas supply and to draw in air, the Base to support the burner so that it will not topple. Now, we have finished with this basec review of practical two. Now, i would proceed with a phenomena, related to Bunsen Burner but more connected to electricity. Watch the video below to learn more:

Wasnt it amazing that he managed to light the Bunsen Burner with only his fingers? The answer is actually no. Although it may seem to be very amazing, there is a very simple explanation to it. You can see that in the video, the students were all joining hands and the last person joined hands with the blue shirted girl and her hand was on something called the Van De Graaf Generator. Now, i will tell you guys more about the generator.

Van De Graaf Generator

A Van de Graaff generator is an electrostatic generator which uses a moving belt to accumulate very high electrostatically stable voltages on a hollow metal globe on the top of the stand. It was invented in 1929 by American physicist Robert J. Van de Graaff. The Van de Graaff generator can be thought of as a constant-current source connected in parallel with a capacitor and a very large electrical resistance.

A simple Van de Graaff-generator consists of a belt of silk, or a similar flexible material, running over two metal pulleys, one of which is surrounded by a hollow metal sphere. Two electrodes in the form of comb-shaped rows of sharp metal points, are positioned respectively near to the bottom of the lower pulley and inside the sphere, over the upper pulley. One Comb is connected to the sphere, and the other comb  to the ground. A high DC potential (with respect to earth) is applied to the roller ; a positive potential in this example.

As the belt passes in front of the lower comb, it receives negative charge that escapes from its points due to the influence of the electric field around the lower pulley, which ionizes the air at the points. As the belt touches the upper roller, it transfers some electrons, leaving the roller with a negative charge, which added to the negative charge in the belt generates enough electric field to ionize the air at the points of the upper comb. Electrons then leak from the belt to the upper comb and to the terminal, leaving the belt positively charged as it returns down and the terminal negatively charged. The sphere shields the upper roller and comb from the electric field generated by charges that accumulate at the outer surface of it, causing the discharge and change of polarity of the belt at the upper roller to occur practically as if the terminal were grounded. As the belt continues to move, a constant charging current travels via the belt, and the sphere continues to accumulate negative charge until the rate that charge is being lost equals the charging current. The larger the sphere and the farther it is from ground, the higher will be its final potential.

Since a Van de Graaff generator can supply the same small current at almost any level of electrical potential, it is an example of a nearly ideal current source. The maximum achievable potential is approximately equal to the sphere's radius multiplied by the e-field where corona discharges begin to form within the surrounding gas.

Now, let us connect this to the video shown, when the teacher touched the small Van De Graaf Generator, a small change passed through here body, transfering to the other students and finally to the last person whow as the one to light up the bunsen burner. As there was a small charge inside his body. (Static electricity), Bunsen Burners, just need a small spark to light it up and in daily life, people use, match sticks or lighters are used. When the guy moved his hands close to the Bunsen Burner, as it was made of metal, there was a spark which came fromt eh guys finger when his hand came into close range of the burner's barrel, the small charge then ignited the Burner. This is a cool experiment i found out about the burner, i have finished giving the explanation and as i end my post here, i urge people not to try out the siilar experiment because, you may get yourself burned in the process! This post will include practicals two and three because they are both linked together.Read on to the next practical!