Q19 of 31 Page 19

AB is a potentiometer wire (Fig 3.4). If the value of R is increased, in which direction will the balance point J shift?


As the resistance R increases, current I through the circuit decreases.


This decreases the potential difference across the potentiometer which results in decrease in the potential gradient k across AB.


At balance point,


As k decreases, length l increases for a constant emf E.


Hence, the balance point moves towards B.


More from this chapter

All 31 →
17

Why are alloys used for making standard resistance coils?

 18

Power P is to be delivered to a device via transmission cables having resistance RC. If V is the voltage across R and I the current through it, find the power wasted and how can it be reduced.

 20

While doing an experiment with potentiometer (Fig 3.5) it was found that the deflection is one sided and (i) the deflection decreased while moving from one end A of the wire to the end B; (ii) the deflection increased. While the jockey was moved towards the end B.


(i) Which terminal +or –ve of the cell E1, is connected at X in case (i) and how is E1 related to E?


(ii) Which terminal of the cell E1 is connected at X in case (ii)?


 21

A cell of emf E and internal resistance r is connected across an external resistance R. Plot a graph showing the variation of P.D. across R, verses R.