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What is the resultant resistance of the circuit given above

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What is the resultant resistance of the circuit given above

What is the resultant resistance of the circuit given above?

A. 8Ω

B. 11Ω

C. 4Ω

D. 3.6Ω

QUICK ANSWER…

A

EXPLANATION…

If a number of resistors are arranged in series, the effective or resultant resistance of them combined is simply addition of the resistance of each resistor.

But if a number of resistors are connected in parallel, the reciprocal of the effective or resultant resistance will be the simple addition of the reciprocal of the resistance of each resistor. Please note that reciprocal here means inverse.

If R1, R2, R3, and R4 are connected in series, then:

Resultant resistance = R1 + R2 + R3 + R4

If they are connected in parallel, then:

1/Resultant resistance = 1/R1 + 1/R2 + 1/R3 + 1/R4

In the above connection, two of the 2ohms resistors are connected in parallel, we would have to resolve them first, so that the resultant of these two resistors will now be in series with the 4 and 3 ohms resistors.

Resultant resistance of the two 2ohms resistors will be calculated thus:

1/R = ½ + ½ ,

Therefore, 1/R = 2/2 = 1/1, R = 1

We now have three resistors in series which are, 3 ohms, 1 ohms, and 4 ohms.

Final resultant resistance will be = 3 + 1 + 4 = 8 ohms.

Now for the right answer to the above question:

  1. Option A is correct.
  2. Option B is incorrect.
  3. C is incorrect.
  4. D is not the correct answer.

HELPFUL TIPS…

You may please note these/this:

  • In series connection, the positive terminal of one resistor is directly connected to the negative terminal of the next resistor.
  • In parallel connection, all the positive terminals of each resistor are connected together to the negative terminal of the voltage source, and all the negative terminals of each resistor are connected together to the positive side of the voltage source.

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/culled from 2018 JAMB-UTME physics question 6 /

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