Which of the following statements is incorrect?

The number of unpaired electrons in an $O_2$ molecule is

In the figure shown,for given values of $R_1$ and $R_2$,the balance point for the jockey is at $40\, cm$ from $A$. When $R_2$ is shunted by a resistance of $10\,\Omega$,the balance point shifts to $50\, cm$. Find $R_1$ and $R_2$ $(AB = 1\, m)$.

Which one of the following is heterosporous?

After absorbing a slowly moving neutron of mass $m_N$ (momentum $\sim 0$),a nucleus of mass $M$ breaks into two nuclei of masses $m_1$ and $5m_1$ $(6m_1 = M + m_N)$. If the de-Broglie wavelength of the nucleus with mass $m_1$ is $\lambda$,then the de-Broglie wavelength of the other nucleus will be:

Two circular coils can be arranged in any of the three situations shown in the figure. Their mutual inductance will be