The region between two concentric spheres of radii '\(a\)' and '\(b\)' , respectively (see figure), has volume charge density \(\rho=\frac{A}{r}\), where \(A\) is a constant and \(r\) is the distance from the centre. At the centre of the spheres is a point charge \(Q\). The value of \(A\) such that the electric field in the region between the spheres will be constant, is:
1. \( \frac{Q}{2 \pi a^2} \)
2. \(\frac{Q}{2 \pi\left(b^2-a^2\right)} \)
3. \(\frac{2 Q}{\pi\left(a^2-b^2\right)} \)
4. \(\frac{2 Q}{\pi a^2}\)
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| 1. | \(\phi_1=\phi_2=\phi_3=\phi_4 \) | 2. | \(\phi_1>\phi_3;~\phi_2<\phi_4 \) |
| 3. | \(\phi_1>\phi_2>\phi_3>\phi_4 \) | 4. | \(\phi_1<\phi_2=\phi_3>\phi_4 \) |
A point charge of \(+12~\mathrm{\mu C}\) is at a distance \(6\) cm vertically above the centre of a square of side \(12\) cm as shown in figure. The magnitude of the electric flux through the square will be:
1. \( 226 \times 10^2 ~\frac{\mathrm{Nm}^2}{\mathrm{C}}\)
2. \( 226 \times 10^3 ~\frac{\mathrm{Nm}^2}{\mathrm{C}}\)
3. \(326 \times 10^3 ~\frac{\mathrm{Nm}^2}{\mathrm{C}}\)
4. \( 326 \times 10^2 ~\frac{\mathrm{Nm}^2}{\mathrm{C}}\)