Each element in the finite chain of resistors shown in the figure is $1\,\Omega$. $A$ current of $1\,A$ flows through the final element. What is the potential difference $V$ across the input terminals of the chain in $volt$?

At a certain temperature,$\operatorname{rod} A$ and $\operatorname{rod} B$ of different materials have lengths $L_A$ and $L_B$ respectively. Their coefficients of linear expansion are $\alpha_A$ and $\alpha_B$ respectively. It is observed that the difference between their lengths remains constant at all temperatures. The ratio $L_{A}: L_{B}$ is given by

Current $I$ is flowing in a conductor shaped as shown in the figure. The radius of the curved part is $r$ and the length of the straight portions is very large. The value of the magnetic field at the centre $O$ will be

In contrast to annelids,the Platyhelminthes show:

The electric current $i$ in the circuit shown is (in $A$)

Which of the following is incorrect with respect to $Chondrichthyes$?