An electric kettle has two coils. When one coil is switched on,the tea gets heated in $10 \, \text{min}$. When the other coil is switched on,the same amount of tea gets heated in $40 \, \text{min}$. If both coils are connected in parallel,how long will it take to heat the same amount of tea (in $, \text{min}$)?

Two resistors with resistances $R_1$ and $R_2$ are connected in series and two capacitors with capacitances $C_1$ and $C_2$ are also connected in series. These two systems are connected to a battery of $EMF$ $\varepsilon$ as shown in the figure. The potential difference between points $a$ and $b$ is zero in the steady state if:

$A$ thermocouple develops $200\,\mu V$ between $0\,^{\circ}C$ and $100\,^{\circ}C$. If it develops $64\,\mu V$ and $76\,\mu V$ respectively between $(0\,^{\circ}C - 32\,^{\circ}C)$ and $(32\,^{\circ}C - 70\,^{\circ}C)$,then what will be the thermo-emf it develops between $70\,^{\circ}C$ and $100\,^{\circ}C$ in $\mu V$?

Which one of the following is not a correct statement?

Statement $(I)$: The temperature coefficient of resistance for most metals in pure form is positive.
Statement $(II)$: $A$ metal wire $2 \ mm$ in diameter carries a charge of $360 \pi \ C$ in two hours. If the metal contains $5 \times 10^{22}$ free electrons $/ cm^3$, then the drift velocity of the electrons in the wire is $6.25 \times 10^{-6} \ m/s$.
Statement $(III)$: Semiconductors like pure germanium do not obey Ohm's law for all ranges of electric field values. Which of the following is correct?

Two current elements $P$ and $Q$ have current-voltage characteristics as shown below:
Which of the graphs given below represents the current-voltage characteristics when $P$ and $Q$ are in series?