A circular coil, carrying current, has radius $R$. The distance from the centre of the coil on the axis where the magnetic induction will be $\frac{1}{27}$ th of its value at the centre of the coil is
$2 \sqrt{2} R$
$3 \sqrt{2} R$
$3 R$
$2 \sqrt{3} R$
A square of side $L$ lies in the $x-y$ plane,where the magnetic field is given by $B=B_0(2 \hat{i}+3 \hat{j}+4 \hat{k})$ where $B_0$ is constant.The magnetic flux passing through the square is $L$
$5 B_0 L^2$
$3 B_0 L^2$
$2 B_0 L^2$
$4 B_0 L^2$
A resistor of resistance'$R$'draws power'$P$'when connected to an AC source.If an inductance is now placed in series with $R$ ,such that the impedance of the circuit becomes'$Z$',the power drawn will be
$P\left(\frac{R}{Z}\right)$
$P\left(\frac{R}{Z}\right)^3$
$P\left(\frac{R}{Z}\right)^2$
$P \sqrt{\frac{Z}{R}}$
A simple pendulum of length $l$ has a bob of mass $m$ ,with a charge $q$ .On it a vertical sheet of charge, with surface charge density'$\sigma$'passes through the point of suspension.At equilibrium,if the string makes an angle $\theta$ with the vertical,then
$\tan \theta=\frac{\sigma q}{2 \varepsilon_0 m g}$
$\tan \theta=\frac{\sigma q}{\varepsilon_0 m g}$
$\cot \theta=\frac{\sigma q}{2 \varepsilon_0 m g}$
$\cot \theta=\frac{\sigma q}{\varepsilon_0 m g}$
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