Electronics - Parallel Circuits - Discussion
Discussion Forum : Parallel Circuits - General Questions (Q.No. 20)
20.
What are the individual values of two parallel resistors whose RT is 8 ohms, when one has double the resistance of the other?
Discussion:
15 comments Page 2 of 2.
Pre said:
9 years ago
As per condition given r1 = 2r2.
R total = r1*r2/r1 + r2.
=> 2r1 * r1/3r1 (r1 and r1 get cancelled).
Then,
=> 2r1/3 = R total = 8.
Then,
r1 = 8 * 3/2,
=> 4 * 3,
=> 12.
Then, r2 = 24.
So the answer is D.
R total = r1*r2/r1 + r2.
=> 2r1 * r1/3r1 (r1 and r1 get cancelled).
Then,
=> 2r1/3 = R total = 8.
Then,
r1 = 8 * 3/2,
=> 4 * 3,
=> 12.
Then, r2 = 24.
So the answer is D.
Mani said:
7 years ago
Given R total=8ohms,
Condition R1=r,
R2=2r.
R1&R2 are connected in parallel,
R total=R1*R2/R1+R2,
8=r*2r/r+2r,
r=12,
R1=r=12,
R2=2r=2*12=24.
Condition R1=r,
R2=2r.
R1&R2 are connected in parallel,
R total=R1*R2/R1+R2,
8=r*2r/r+2r,
r=12,
R1=r=12,
R2=2r=2*12=24.
(1)
Hani said:
6 years ago
Great, helpful, Thanks @Mamata.
Paul said:
6 years ago
Remember, the total Resistance for a Parallel Network is always lesser than the smallest value of the resistance in the network.
Then just reverse Engineer the values from options C & D, applying the product over sum since there are only two resistors in the network to get the total Resistance.
For C (8 & 10).
R = (8*10)/(8+10) = 4.444.
for D (12 & 24),
R = (12*24)/(12+24) = 8.
Option D, has R total of 8 ohms, so the answer is correct, D.
Then just reverse Engineer the values from options C & D, applying the product over sum since there are only two resistors in the network to get the total Resistance.
For C (8 & 10).
R = (8*10)/(8+10) = 4.444.
for D (12 & 24),
R = (12*24)/(12+24) = 8.
Option D, has R total of 8 ohms, so the answer is correct, D.
Umair said:
4 years ago
@Jessi.
If there are three and the same condition is given then how can you define?
If there are three and the same condition is given then how can you define?
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