1.

Derive the relation 1/R=1/R_1+1/R_2+1/R_3 when resistors are joined in parallel.

Answer»

Solution :In parallel combination of THREE resistances `R_1,R_2 and R_3` the current in each of the resistances is different. IF l is the current drawn from the CELL then it is divided into branches `I_1,I_2 and I_3`
Thus, `I=I_1+I_2+I_3`
The potential difference ACROSS each of these resistances is the same.
Thus, from Ohm law `I_1=V/R_1,I_2=V/R_2,I_3=V/R_3`
IF R is the EQUIVALENT resistance then,
`I=V/R`
`therefore V/R=V/R_1+V/R_2+V/R_3`
and `1/R=1/R_1+1/R_2+1/R_3`


Discussion

No Comment Found

Related InterviewSolutions