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A circuit has a section ABC if the poten...

A circuit has a section `ABC` if the potential at point `A,B and C` are `V_(1) , V_(2) and V_(3)` respectively , calculate the potential at point `O`

A

`V_(1)+V_(2)+V_(3)`

B

`[(V_(1)+V_(2)+V_(3))/(R_(1)+R_(2)+R_(3))][(1)/(R_(1)+R_(2)+R_(3))]^(-1)`

C

zero

D

`[(V_(1)+V_(2)+V_(3))/(R_(1)+R_(2)+R_(3))](R_(1)+R_(2)+R_(3))`

Text Solution

Verified by Experts

The correct Answer is:
B

Applying juction rule `-I_(1)-I_(2)-I_(3)=0`
i.e., `I_(1)+I_(2)+I_(3)=0…(i)`
Let, `V_(0)` bet the potential at point O. By Ohm's law for resistance, `R_(1),R_(2) and R_(3)` respectively, we get
`(V_(0)-V_(1))=I_(1)R_(1),(V_(0)-V_(2))=I_(2)R_(2) and (V_(0)-V_(3))=I_(3)R_(3)`
`or I_(1)=((V_(0)-V_(1)))/(R_(1)), I_(2)=((V_(0)-V_(2)))/(R_(2)), I_(3)=((V_(3)-V_(3)))/(R_(3))`
So substituting these values of `I_(1),I(2) and I_(3)` in eq. (i) , we get
`V_(0)[(1)/(R_(1))+(1)/R_(2)+(1)/(R_(3))]-[(V_(1))/(R_(1))+(V_(2))/(R_(2))+(V_(3))/(R_(3))]=0`
`V_(0)=[(V_(1))/(R_(1))+(V_(2))/(R_(2))+(V_(3))/(R_(3))] [(1)/(R_(1))+(1)/R_(2)+(1)/(R_(3))]^(1)`
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