NCERT Class XII Chapter
Current Electricity
Questions With Solutions
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Question : 23
Total: 24
Figure shows a potentiometer circuit for comparison of two resistances. The balance point with a standard resistor R = 10.0 Ω is found to be 58.3 cm, while that with the unknown resistance X is 68.5 cm. Determine the value of X. What might you do if you failed to find a balance point with the given cell of emf ε?
Solution:
For comparison of resistances, R and X should be in series and same current should flow through them.
IR =k l 1
I (10) = k × 58.3
IX =k l 2
IX = k × 68.5
∴
X = 11.75 Ω
If we fail to find balance point with cell of e.m.f. e, in that case we should reduce the current I and for that e.m.f. ε of cell responsible for current I should reduce, or a resistor can also be attached in series with R and X to reduce current.
IR =
I (10) = k × 58.3
IX =
IX = k × 68.5
∴
X = 11.75 Ω
If we fail to find balance point with cell of e.m.f. e, in that case we should reduce the current I and for that e.m.f. ε of cell responsible for current I should reduce, or a resistor can also be attached in series with R and X to reduce current.
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