Companion cells are closely associated with $..........$.

An infinite number of electric charges each equal to $5 \text{ nC}$ (magnitude) are placed along the $X$-axis at $x=1 \text{ cm}, x=2 \text{ cm}, x=4 \text{ cm}, x=8 \text{ cm} \dots$ and so on. In this setup, if the consecutive charges have opposite signs, then the electric field in $\text{N/C}$ at $x=0$ is: $\left(\frac{1}{4 \pi \varepsilon_0}=9 \times 10^9 \text{ N} \cdot \text{m}^2/\text{C}^2\right)$

If $(1+x)^{15}=a_0+a_1 x+\ldots+a_{15} x^{15}$,then $\sum_{r=1}^{15} r \frac{a_r}{a_{r-1}}$ is equal to

$A$ steady current flows in a long wire. It is bent into a circular loop of one turn and the magnetic field at the centre of the coil is $B$. If the same wire is bent into a circular loop of $n$ turns,the magnetic field at the centre of the coil is

$A$ steel wire can withstand a load up to $2940 ~N$. $A$ load of $150 ~kg$ is suspended from a rigid support. The maximum angle through which the wire can be displaced from the mean position,so that the wire does not break when the load passes through the position of equilibrium,is (in $^{\circ}$)

Which of the following values indicates hypertension?