For a transistor, $\alpha_{\mathrm{dc}}$ and $\beta_{\mathrm{dc}}$ are the current ratios, then the value of $\frac{\beta_{\mathrm{dc}}-\alpha_{\mathrm{dc}}}{\alpha_{\mathrm{dc}} \times \beta_{\mathrm{dc}}}$

Two coils P and Q are kept near each other. When no current flows through coil P and current increases in coil Q at the rate $10 \mathrm{~A} / \mathrm{s}$, the emf in coil P is 12 mV . When coil Q carries no current and current of 1.5 A flows through coil P , the magnetic flux linked with the coil Q in mWb is

A mass ' M ' is suspended by a rope from a rigid support at point ' P ' as shown in figure. Another rope is tied at end ' Q ' and pulled horizontally with a force ' $F$ '. If the rope makes an angle ' $\theta$ ' with vertical then the tension in the string ' PQ ' is

A mass ' $M$ ' attached to a horizontal spring executes S.H.M. of amplitude $A_1$. When the mass M passes through its mean position, then a smaller mass ' $m$ ' is placed over it and both of them move together with amplitude $\mathrm{A}_2$. The ratio $\left(\frac{A_1}{A_2}\right)$ is