- In a metre bridge [Fig. 3.27], the balance point is found to be at 39.5 cm from the end A, when the resistor Y is of $12.5\ \Omega.$ Determine the resistance of X. Why are the connections between resistors in a Wheatstone or meter bridge made of thick copper strips?
- Determine the balance point of the bridge above if X and Y are interchanged.
- What happens if the galvanometer and cell are interchanged at the balance point of the bridge? Would the galvanometer show any current?
Exercise
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- Given,
Standard known resistance, $\text{S}=\text{Y}=12.5\ \Omega$
We have to determine the unknown resistance, R = X
Using the relation for balance condition we get,
$\text{S}=\frac{100-1}{1}\times\text{R}$
$\therefore\ \ 12.5=\frac{100-39.5}{39.5}\times\text{X}$
$\text{X}=\frac{12.5\times39.5}{60.5}=8.16\ \Omega$
Thick copper strips helps to minimise resistance of the connections and hence they are used.
- If, X and Y are interchanged,then, lengths are also interchanged.
- If the galvanometer and cell are interchanged, the position of the balance point remains unchanged. Hence, the galvanometer will show no current.
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