$A$ student is to answer $10$ out of $13$ questions in an examination such that he must choose at least $4$ from the first $5$ questions. The number of choices available to him is

$A$ graph of magnetic flux $\phi$ versus current $(I)$ is shown for four inductors $A, B, C, D$. The inductor with the smallest value of self-inductance is:

Which of the following is a self-adjusting force?

The equations $x-y=4$ and $x^2+4xy+y^2=0$ represent the sides of a/an

$2, 3$-dimethylhexane contains tertiary,secondary,and primary carbon atoms,respectively:

$\Delta \lambda$ is the difference between the wavelength of the $K_{\alpha}$ line and the minimum wavelength of the continuous $X$-ray spectrum when the $X$-ray tube is operated at a voltage $V$. If the operating voltage is changed to $V/3$,then the above difference is $\Delta \lambda^{\prime}$. Then: