An electronic device operates at 2 MHz . The oscillating circuit has an inductance $20 \times 10^{-5} \mathrm{H}$. What is the capacitive reactance of the resonant circuit?
$251.2 \Omega$
$2512 \Omega$
$1256 \Omega$
$5024 \Omega$
A singer, during his performance, stands on the edge of a circular turntable, and begins to walk along its edge with a speed of $1.5 \mathrm{~ms}^{-1}$ relative to the ground. The turn table is mounted on a frictionless vertical axle. Its radius R =3m and its moment of inertia about the axle is $150 \mathrm{~kg} \mathrm{~m}^2$. It is initially at rest. If the mass of the singer is 75 kg , the time taken by the man to complete one revolution is:
12.57 s
8.56 s
6.28 s
20.5 s
A pith ball of mass ' $m$ ' gram and charge ' $Q$ ' is suspended using a mass less silk thread near a large charged conducting metal sheet of area ' $A$ ' and surface charged density ' $\sigma$ '. If the silk thread makes an angle $\Theta$ with the metal sheet, then:
$\tan \theta \propto \sigma$
$\tan \theta \propto A$
$\tan \theta \propto m g$
$\tan \theta \propto \frac{1}{\sigma}$
The material selected for making a permanent magnet should have:
High coercivity, low permeability and high retentivity
Low coercivity, low permeability and low retentivity
Low coercivity, low permeability and high retentivity
High coercivity, high permeability and high retentivity
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