• # question_answer Teacher was demonstrating an experiment on potentiometer to the students of class 12th. While doing the experiment (figure), it was found that the deflection is one sided and (a) the deflection decreased while moving from one end A of the wire, to the end B; (b) the deflection increased, while the jockey was moved towards the end B. The students asked the reason behind the deflection. Teacher then happily explained the reason to the students. They all felt satisfied after knowing the reason. (i) What values are displayed by the teacher? (ii) Which terminal positive or negative of the cell ${{E}_{1}}$ is connected at X in case (a) and how is  ${{E}_{1}}$ related to E? (iii) What is the advantage of using thick metallic strips to join wires in a potentiometer?

 (i) Scientific temperament, responsibility, perseverance and dutifulness. (ii) The deflection in galvanometer is one sided and the deflection decreased, while moving from one end A of the wire to the end B, its imply that current in auxiliary circuit (lower circuit containing primary cell) decreases, while potential difference across A and jockey increases. This is possible only when positive terminal of the cell ${{E}_{1}}.$ is connected at X and ${{E}_{1}}>E.$ (iii) The resistance of thick metallic strips is extremely small and hence negligible.