Question

how do you calculate the effective resistance in a parallel circuit

Answer 1

You take the inverse of the total resistances of each branch and add them up.
So if you have 5ohm, 7 ohm, and 10ohm, you would add

1/5 + 1/7 + 1/10 = 31/70

Then flip it back by either using the \[x^{-1}\] (inverse) key on your calculator or simply dividing 70 by 31 to get a total of 2.26ohms

Answer 2

In the simple case where there are only two resistors in parallel this simplifies to:
\[R _{p}=(R_{1}\times R _{2})/(R _{1}+ R _{2})\]

Answer 3

In a parellel circuit we calculate the effective resistance
by summing up all the \[1/given Resistances\] which gives the result \[1/effective Resistance\]and taking its reciprocal gives the answer.
Example is as cited above.
Let \[R _{1},R _{2},R _{3}......R _{n}\] be the given resistances
1/Effective resistance (R)=\[1/R _{1}+1/R _{2}+1/R _{3}+........1/R _{n}\]
, Simplifying and taking the reciprocal will give the effective resistance R
If there is 2 resistance only effective resistance will be calculated as MECHASTEVE wrote.

Answer 4

do remember that the effective resistance of a parallel connection is always less than any of the individual resistances of resistors in parallel.

Answer 5

by taking reciprocal of total resistances in the circuit and add up them
e.g, let three resistances of 3ohm,7ohmand2ohm
now,the effective resistance=1/3+1/7+1/2=41/42

Answer 6

harjit, don't forget to take to inverse of the final answer to get the correct value. :)