2. Questions Bank
  3. 10th Class
  4. Science
  5. Electricity and Circuits

10th Class Science Electricity and Circuits Question Bank Electricity

  • question_answer
    The circuit shown in figure was set up to determine the emf of a thermo cell. As P is moved away from X to Y, the galvanometer deflection is always in the same direction but decrease continuously until Y is reached. In order to obtain a balance point between X and Y, it is necessary to

    A)  decreases R  

    B)  increases R

    C)  reverse the terminals of E

    D)  interchange the hot and cold junctions

    Correct Answer: A

    Solution :

     Since balance is not obtained even at the end of potentiometer wire, the drop across the wire due to primary emf\[E\]is less than the emf being measured. It is so because a large part of the voltage \[E\]gets dropped across the series resistance\[R\]. To increase the voltage drop across the potentiometer wire, current flowing through the potentiometer wire should be increased, for this the total resistance of the primary circuit should be decreased. Resistance of the potentiometer wire is constant, so series resistance\[R\]should be decreased. (\[IR\]should not be used to think about the drop across\[R\], because neither \[R\]nor\[I\]is constant).


You need to login to perform this action.
You will be redirected in 3 sec spinner