The temperature of the hot junction of a thermocouple changes from $80\,^{\circ}C$ to $100\,^{\circ}C$. The percentage change in thermoelectric power is ............... $\%$.

$A$ star initially has $10^{40}$ deuterons. It produces energy via the processes:
${}_1H^2 + {}_1H^2 \to {}_1H^3 + p$
${}_1H^2 + {}_1H^3 \to {}_2He^4 + n$
The masses of the nuclei are as follows: $M(H^2) = 2.014 \, amu$,$M(p) = 1.007 \, amu$,$M(n) = 1.008 \, amu$,$M(He^4) = 4.001 \, amu$. If the average power radiated by the star is $10^{16} \, W$,the deuteron supply of the star is exhausted in a time of the order of:

The uncertainties in the velocities of two particles $A$ and $B$ are $0.05 \ m/s$ and $0.02 \ m/s$ respectively. The mass of $B$ is five times that of mass $A$. What is the ratio of uncertainties $\left(\frac{\Delta x_A}{\Delta x_B}\right)$ in their positions?

If $x$ is real, then the minimum value of $\frac{x^2-x+1}{x^2+x+1}$ is

Raoult's law is obeyed by each constituent of a binary liquid solution when

The centre of mass of a body