Vehicles carrying highly inflammable materials have chains hanging to the ground. Explain.

Explanation

Consider the situation as shown in the figure . Let a charge q is placed at mid-point (M) of side. BC . For charge q to be at equilibrium , we have
` F = ( 9 xx 10 ^(9) xx 2 xx 3 xx 10 ^(-12))/((0.2)^(2)) cos 30 ^(@) and 2 xx F =F.`
` therefore " " F. = 2 xx 1.169 = (9 xx 10 ^(9) xx 2 xx q xx 10 ^(-6))/((0.10)^(2))`
` rArr " " q= 2.25 sqrt3 muC `