Question

In the figure shown the plates of a parallel plate capacitor have unequal charges. Its capacitance is ‘C’ P is a point outside the capacitor and close to the plate of charge –Q. The distance between the plates is ‘d’ select incorrect alternative

• A. A point charge at point ‘P’ will experience electric forcé dueto capacitor
• B. The potencial difference between the plates will be 3Q/2C
• C. The energy stored in the electric field in the región between the plates is
• D. The forcé on one plate due to the other plate is

Answer 1

Answer: (D)

The forcé on one plate due to the other plate is

Answer 2

$\mathrm { E } = \frac { 2 \mathrm { Q } } { 2 \mathrm {~A} \varepsilon _ { 0 } } + \frac { \mathrm { Q } } { 2 \mathrm {~A} \varepsilon _ { 0 } } \Rightarrow \mathrm { E } = \frac { 3 \mathrm { Q } } { 2 \mathrm {~A} \varepsilon _ { 0 } }$

(ii) F = EQ/2

$\mathrm { F } = \left( \frac { 2 \mathrm { Q } } { 2 \mathrm {~A} \varepsilon _ { 0 } } \right) \times \frac { ( - \mathrm { Q } ) } { 1 } = \frac { - \mathrm { Q } ^ { 2 } } { \mathrm {~A} \varepsilon _ { 0 } }$

$\mathrm { F } = \frac { \mathrm { Q } ^ { 2 } } { \mathrm {~A} \varepsilon _ { 0 } }$

(iii) Energy = $\frac { 1 } { 2 }$ e₀ E² Ad

$= \frac { 1 } { 2 } \varepsilon _ { 0 } \left( \frac { 3 \mathrm { Q } } { 2 \mathrm {~cd} } \right) ^ { 2 }$ Ad =