1.

A, B, and C are three large, parallel conducting plates, placed horizontally. A and C are rightly fixed and earthed in figure . B is given some charge . Under the electorstatic and gravitational forces, B may be

Answer»

in equilibrium if it is CLOSER to A than to C
in equilibrium midway between A and C
B can never be in stable equilibrium .
in equilibrium if it is closer to C than to A.

Solution :a.,c.
As `A` and `C` are EARTHED, they are connected to each other. Hence, `'A+B'` and `'B+C'` are two capacitors with the same potential difference. If `B` is closer to `A` than to `C`, then the CAPACITANCE `C_(AB)gtC_(BC)`. The upper surface of `B` will have greater charge than the lower surface. As the force of attraction between the plates of a CAPACITOR is proportional to `Q^(2)`, there will be a net upward force on `B`. This can balance its weight.


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