In case of a fire, before the firemen use the water hoses, they shut off the main electrical supply for the area. Explin why they do this.

In case of a fire , before the fireman use the water hoses , they shut off the main electrical supply for the area. Explain why they do this.

Two vessels have the same base area but different shapes. The first vessel takes twice the volume of water that the second vessel requires to fill upto a particular common height. Is the force exerted by the water on the base of the vessel the same in the two cases ? If so, why do the vessels filled with water to thatsame height give different readings on a weighing scale ?

Two vessels have the same base area but different shapes. the first vessel takes twice the volume of water than the second, vessel requires to fill upto a particular common height. Is the force exerted by water on the base of the vessel the same in the two cases? If so, why do the vessel filled with water to that same height give differnt readings on a weighing scale?

Give reason : Water is not used to control fire involving electrical equipment.

Investigate: Use strips nad fasteners to make a triangle and a quadrilateral. Try to push inward at any one vertex of the triangle.Do the same to the quadrilateral. Is the triangle distorted ?Is the quadrilateral distorted?Is the triangle rigid? Why is it that structures like electric towers make use of triangular shapes and not quadrilaterals?

Using Gauss's theorem, show mathematically that for any point outside the shell, the field due to a uniformly chargead thin spherical shell is the same as if the entire charge is concentrated at the centre. Why do you expect the electric field inside the shell to be zero according to this theorem?