Electrostatics
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Two isolated conducting spheres S₁ and S₂ of radius (2/3)R and (1/3)R have 12µC and -3 µC charges, respectively, and are at a large distance from each other. They are now connected by a conducting wire. A long time after this is done the charges on S₁ and S₂ are respectively:
Two isolated conducting spheres S₁ and S₂ of radius (2/3)R and (1/3)R have 12µC and -3 µC charges, respectively, and are at a large distance from each other. They are now connected by a conducting wire. A long time after this is done the charges on S₁ and S₂ are respectively:
When the two conducting spheres are connected by a wire, they will reach the same electric potential, V.
The total charge Q_total = 12µC + (-3µC) = 9µC. This total charge will redistribute.
Let the final charges be q? and q? + q? = 9µC.
The potential of a sphere is V = kq/r.
V? = V?
k q? /R? = k q? /R?
A 5µF capacitor is charged fully by a 220 V supply. It is then disconnected from the supply and is connected in series to another uncharged 2.5µF capacitor. If the energy change during the charge redistribution is X/100 J then value of X to the nearest integer is:
A 5µF capacitor is charged fully by a 220 V supply. It is then disconnected from the supply and is connected in series to another uncharged 2.5µF capacitor. If the energy change during the charge redistribution is X/100 J then value of X to the nearest integer is:
Heat loss; ΔH = U? - U? = 1/2 (C? / (C? +C? ) (V? -V? )²
= 1/2 × (5×2.5)/ (5+2.5) (220-0)²µJ
= 5/ (2×3) × 22×22×100×10? J
= 5×11×22/3 × 10? J = 1210/3 × 10? J = 1210/3 × 10? ³ J × 4 × 10? ²
According to questions
x/100 = 4×10? ²
So, x=4
Note: But given answer by JEE Main x=36



