What is the total resistance in the above diagram?
A. 5 ohms
B. 15 ohms
C. 25 ohms
D. 35 ohms
QUICK ANSWER…
C
DETAILS…
Effective resistance in series = simple addition of each resistance.
Rₑ = R₁ + R₂ + …
Reciprocal of effective resistance in parallel = simple addition of the reciprocal of each resistance.
1/ Rₑ = 1/ R₁ + 1/ R₂ + ….
For this problem, observe that there are two resistors in parallel, we must firstly resolve this, and the effective resistance between these two will now be in series with the two extreme resistors.
For the two parallel resistors,
We now have three resistors in series which are: 10ohms, 5ohms, and 10ohms.
The effective resistance of these three will be:
Rₑ = R₁ + R₂ + R₃
Rₑ = 10 + 5 + 10 = 25 ohms
Now for the right answer to the above question:
- Option A is incorrect.
- Option B is incorrect.
- C is correct.
- D is not the correct answer.
KEY-POINTS…
You may please note these/this:
- Parallel connection occurs where the wire is split as shown in the center of the diagram.
- Series connection occurs when there is no split, I hope my explanation is simple enough.
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/ culled from 2015 JAMB-UTME physics question 3 /
