The number of triangles that can be formed by choosing the vertices from a set of $12$ points,seven of which lie on the same straight line,is

The plates of a parallel plate capacitor are charged up to $100\, V$. $A$ $2\, mm$ thick plate is inserted between the plates. To maintain the same potential difference,the distance between the capacitor plates is increased by $1.6\, mm$. The dielectric constant of the plate is:

The $Dystrophin$ gene contains how many million bases?

In a bicycle,the radius of the rear wheel is twice the radius of the front wheel. If $r_F$ and $r_r$ are the radii,and $v_F$ and $v_r$ are the speeds of the topmost points of the wheels respectively,then:

The magnetic susceptibility of the material of a rod is $499$. Permeability of vacuum is $4 \pi \times 10^{-7} \ H/m$. Absolute permeability of the material of the rod in $H/m$ is:

$A$ student connects a long air-cored coil of manganin wire to a $100\, V$ $D.C.$ supply and records a current of $25\, A$. When the same coil is connected across a $100\, V$,$50\, Hz$ $A.C.$ supply,the current reduces to $20\, A$. The reactance of the coil is ...... $\Omega$.