For Physics Purpose :

The heating effect of an electric current:
When a charge moves in a conductor, work is done by that charge. Devices can be made which convert this work into heat ( electric heaters), light (light bulbs and neon tubes), or motion, i.e. kinetic energy (power tools).
From the definition of potential difference, V, we have V = W/Q, where W is the work done by charge Q. Hence, W = VQ.
Current is the flow of charge, so that in time t, the amount of charge moving through the conductor will be Q = It.
Therefore, W = VIt gives the work done in time t, by a current I, flowing through a conductor across which the potential difference is V.

We use many devices in which electrical energy is converted into heat energy. When electric current is passed through a wire, it is heated up and the electrical energy is converted into heat energy. Devices like the filament of an electric heater, geyser, light bulb etc utlise this 'heating effect of current'.
Why is heat produced when current is passed through a conductor?
A metallic conductor has a large number of free electrons available in it. When a potential difference is applied across the ends of a wire, the free electrons begin to drift from a region of low potential to a region of high potential. These electrons collide with the positive ions (the atoms which have lost their electrons). These collisions transfer the energy of the electron to the positive ions which begin to vibrate more violently. As a result, heat is produced.
The greater the number of electrons flowing per second, the greater will be the rate of collisions and so greater is the heat produced. If the cross sectional area of conductor is greater, collisions are avoided and hence less heat is produced.

http://www.youtube.com/watch?v=YnMP1Uj2nz0&eurl=http%3A%2F%2Fwww%2Eustudy%2Ein%2Fnode%2F1906&feature=player_embedded

Tungsten, also known as wolfram, is a chemical element with the chemical symbol W and atomic number 74.
A steel-gray metal, tungsten is found in several ores, including wolframite and scheelite. It is remarkable for its robust physical properties, especially the fact that it has the highest melting point of all the non-alloyed metals and the second highest of all the elements after carbon. Tungsten is often brittle and hard to work in its raw state; however, if pure, it can be cut with a hacksaw. The pure form is used mainly in electrical applications, but its many compounds and alloys are used in many applications, most notably in incandescent light bulb filaments, X-ra tubes (as both the filament and target), and superalloys. Tungsten is also the only metal from the third transition series that is known to occur in biomolecules, and is the heaviest element known to be used by living organisms.