First,a set of $n$ equal resistors of $10 \; \Omega$ each are connected in series to a battery of emf $20 \; V$ and internal resistance $10 \; \Omega$. $A$ current $I$ is observed to flow. Then,the $n$ resistors are connected in parallel to the same battery. It is observed that the current is increased $20$ times. The value of $n$ is .... .

If for a thermocouple ${T_n}$ is the neutral temperature,${T_c}$ is the temperature of the cold junction,and ${T_i}$ is the temperature of inversion,then:

Antimony and bismuth are usually used in a thermocouple,because

If $E$ denotes the electric field in a uniform conductor,$I$ the corresponding current through it,${v_d}$ the drift velocity of electrons,and $P$ the thermal power produced in the conductor,then which of the following graphs is incorrect?

$A$ wire of length $L$ and $3$ identical cells of negligible internal resistances are connected in series. Due to current,the temperature of the wire is raised by $\Delta T$ in a time $t$. $A$ number $N$ of similar cells is now connected in series with a wire of the same material and cross-section but of length $2L$. The temperature of the wire is raised by the same amount $\Delta T$ in the same time $t$. The value of $N$ is

The resistance of a wire is $10^{-6} \, \Omega$ per meter. It is bent in the form of a circle of diameter $2 \, m$. A wire of the same material is connected across its diameter. The total resistance across its diameter $AB$ will be