The Total solution for NCERT class 6-12
Answer - 21 : - For comparison of resistances, R and x shouldbe in series and same current should flow through them.
and for that e.m.f.E of cell responsible for current I should reduce, or a resistor can also beattached in series with R and x to reduce current.
Answer - 22 : - In the open circuit, the balance point isobtained for the emf of 1.5 V.