Which of the following molecules has a zero dipole moment?

The resistance of a wire is $R$. It is bent at the middle by $180^{\circ}$ and both the ends are twisted together to make a shorter wire. The resistance of the new wire is

The correct order of reactivity of hydrogen halides with ethyl alcohol is

The ratio of the areas bounded by the curves $y = \cos x$ and $y = \cos 2x$ between $x = 0,$ $x = \pi /3$ and the $x$-axis is:

The input resistance of a common emitter transistor amplifier,if the output resistance is $500 \, k\Omega$,the current gain $\alpha = 0.98$ and power gain is $6.0625 \times 10^6$,is....$\Omega$

$0.066 \ g$ of metal was deposited when a current of $2 \ A$ is passed through a metal ion solution for $100 \ s$. What is the electrochemical equivalent (in $g \ C^{-1}$) of the metal?