A meter bridge is set up as shown to determine an unknown resistance X using a standard 10 ohm resistor. The galvanometer shows null point at 52 cm mark. The end corrections are 1 cm and 2 cm respectively for the ends A and B. The determined value of X is 
An infinitely long straight wire carrying current $I$ is bent in a planar shape as shown in the diagram. The radius of the circular part is $r$. The magnetic field at the centre $O$ of the circular loop is :

The heat generated in 1 minute between points A and B in the given circuit, when a battery of 9 V with internal resistance of 1 \(\Omega\) is connected across these points is ______ J. 