A) \[0.4\,A\]
B) \[-\,0.4\,A\]
C) \[0.8\,A\]
D) \[-\,0.8\,A\]
Correct Answer: B
Solution :
[b] Applying \[{{1}^{st}}\] law of Kirchoffs, \[{{I}_{3}}={{I}_{1}}+{{I}_{2}}\] ...(i) Applying 2nd law of Kirchhoff in Mesh ABCFA \[-30{{I}_{1}}+40-40{{I}_{3}}=0\] ...(ii) in Mesh FCDEF \[40{{I}_{3}}-40-80+40{{I}_{2}}=0\] ...(iii) putting \[{{I}_{3}}\] from (i) in (ii) and (iii) we get \[-30{{I}_{1}}+40-40{{I}_{1}}-40{{I}_{2}}=0\] or, \[-70{{I}_{1}}-40{{I}_{2}}=-40\] or, \[7{{I}_{1}}+4{{I}_{2}}=4\] ...(iv) and \[40{{I}_{1}}+40{{I}_{2}}-40-80+40{{I}_{2}}=0\] or, \[40{{I}_{1}}+80{{I}_{2}}=120\] or, \[4{{I}_{1}}+8{{I}_{2}}=12\] or, \[2{{I}_{1}}+4{{I}_{2}}=6\] ...(v) (iv)\[-\](v) gives \[5{{I}_{1}}=-2\] \[{{I}_{1}}=-0.4\,\,A\]You need to login to perform this action.
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