To measure the temperature coefficient of resistivity \( \alpha \) of a semiconductor, an electrical arrangement shown in the figure is prepared. The arm BC is made up of the semiconductor.The experiment is being conducted at \( 25^\circ \) and resistance of the semiconductor arm is \( 3\,\text{m}\Omega \). Arm BC is cooled at a constant rate of \( 2^\circ\text{C}/\text{s} \). If the galvanometer G shows no deflection after \( 10\,\text{s} \), then \( \alpha \) is:
