Which of the following elements has the least number of electrons in its $M$ shell?

The diameter of the objective of a telescope is $1 \ m$. Its resolving limit for light of wavelength $4538 \ \mathring{A}$ will be:

If $\cos x + \cos^2 x = 1$,then the value of $\sin^2 x + \sin^4 x$ is

If $5x - 12y + 10 = 0$ and $12y - 5x + 16 = 0$ are two tangents to a circle,then the radius of the circle is

$A$ vibration magnetometer consists of two identical bar magnets placed one over the other such that they are perpendicular and bisect each other. The time period of oscillation in a horizontal magnetic field is $2^{5/4} \ s$. One of the magnets is removed and if the other magnet oscillates in the same field,then the time period in seconds is:

An ideal coil of $10\, H$ is connected in series with a resistance of $5\, \Omega$ and a battery of $5\, V$. After $2\, s$,after the connection is made,the current flowing (in ampere) in the circuit is.