Question

Why is the balance point of the meter bridge experiment preferred to be taken in between 30cm and 70cm?

Answer 1

This question demands your prior knowledge on the metre bridge construction as well as working. So, as the first step, you could explain what a meter bridge is and then you could explain its working principle. Recall its working and hence answer the given question.

Complete step-by-step solution:
In order to answer this question, one should first know what a metre bridge really is. It is also known as a slide wire bridge and it works based on the principle of Wheatstone bridge. Metre bridge basically is an instrument that is known to be used for measuring unknown resistance.
Now, let us understand how it works.
This instrument has a metre length wire and after making all the necessary connections we move the jockey over this wire and find the null point for which the galvanometer shows zero reflection.
Now, let us understand why the balance point of this experiment is preferred between 30cm and 70cm. By doing so, the resistance in the four arms becomes of the same order and thereby making the bridge more sensitive. In such a situation, the errors that occur in the measured value of the resistance would comparatively be smaller.

Note: One should note that the range given in the question includes the middle point of a metre length wire. That is the given question could be otherwise be asked as why the balance preferred around the midpoint of a metre bridge. So, we found that the answer has to do with the sensitivity of the instrument in short.