current thru the 5 ohm resistor call I.
Then the current in the varistat must be divided such that current divides:
The total current is I
the resistance across the Parallel branch is R*30/(R+30)
The voltage across the parallel branch is I*R*30/(R+30)
power in the varReistor=Vparall^2/R
so
solve:
Vparallel^2/R=I^2*5
(I*R*30)^2/R(R+30)^2=I^2*5
R*900=5*(R+30)^2
solve for R with the quadratic equation.
A 30 ohm resistor is connected in parallel with a variable resistance R and the parallel combination is then connected in series with a 5 ohm resistor, and connected across 120 volt source. Find the minimum value of R if the power taken by R is equal to the power taken by the 5 ohm resistor.
1 answer
1 answer