$\lim _\limits{x \rightarrow 0} \frac{\sin \left(\pi \cos ^2 x\right)}{x^2}$ is equal to

Which one of the following is the pair of equivalent circuits?

A ferromagnetic material is heated above its curie temperature. The correct statement from the following is that

The number of photoelectrons emitted for light of frequency $v$ (higher than the threshold frequency $\left(v_0\right)$ is proportional to