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16.

A combination of capacitors is set up as shown in the figure. The magnitude of the electric field, due to a point charge Q (having a charge equal to the sum of the charge on the 4 µF and 9 µF capacitors ) at a point distant 30m from it, would equal to

A) 240 N/C

B) 360 N/C

C) 420 N/C

D) 480 N/C

17.

The region between two concentric spheres of radii a and b, respectively (see the figure), has  volume charge density

$\rho =\frac{A}{r}$  where A is a constant and r is distance from the center. 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 sphere will be constant is

A) $\frac{Q}{2\pi a^{2}}$

B) $\frac{Q}{2\pi (b^{2} -a^{2})}$

C) $\frac{2Q}{\pi (a^{2} -b^{2})}$

D) $\frac{2Q}{\pi a^{2} }$

18.

A uniform string of length 20m is suspended from a rigid support. A short wave pulse is introduced at its lowest end. It starts moving up the string. The time taken to reach the support is (Take , g=10 ms-2)

A) $2\pi\sqrt{2}s$

B) 2 s

C) $2\sqrt{2}s$

D) $\sqrt{2}s$

19.

A particle performs simple harmonic motion with amplitude A. Its speed is trebled at the instant that  it is at  a distance

$\frac{2}{3}$  A   from the equilibrium position. The new amplitude  of the  motion is

A) $\frac{A}{3}\sqrt{41}$

B) 3A

C) $A\sqrt{3}$

D) $\frac{7}{3}A$

20.

n moles of an ideal gas undergoes a process A and B shown in the figure. The maximum temperature of the gas during the process will be

A) $\frac{9}{4}\frac{p_{0}V_{0}}{nR}$

B) $\frac{3}{2}\frac{p_{0}V_{0}}{nR}$

C) $\frac{9}{2}\frac{p_{0}V_{0}}{nR}$

D) $\frac{9p_{0}V_{0}}{nR}$

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