A) 0.25 A
B) 0.8 A
C) 0.2 A
D) 0.5 A
Correct Answer: B
Solution :
[b] Key Idea: Potential difference across galvanometer should be equal to potential difference across shunt. |
The shunt and galvanometer are connected as shown in figure. |
Let the total current through the parallel combination is \[i,\] the current through the galvanometer is \[{{i}_{g}}\] and the current through the shunt is \[i-{{i}_{g}}\] |
The potential difference\[{{V}_{ab}}=(\text{ }{{V}_{a}}-{{V}_{b}})\] is the same for both paths, so |
\[{{i}_{g}}G=(i-{{i}_{g}})S\] |
or \[{{i}_{g}}(G+S)=i\,S\] |
or \[\frac{{{i}_{g}}}{i}=\frac{S}{S+G}\] |
The fraction of current passing through shunt \[=\frac{i-{{i}_{g}}}{i}=1-\frac{{{i}_{g}}}{i}\] |
\[=1-\frac{S}{S+G}\] |
\[=\frac{G}{S+G}\] |
\[=\frac{8}{2+8}\] |
\[=\frac{8}{10}=0.8\,A\] |
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