Q25
2 marksVery Short AnswerSection B

(A) Show how you would connect three resistors each of resistance 6Ω6\Omega, so that the combination has a resistance of 9Ω9\Omega. Also justify your answer. OR (B) In the given circuit calculate the power consumed in watts in the resistor of 2Ω2\Omega :

Figure for question 25
Electricity
Electric Circuits
Official Answer

To connect three resistors each of resistance 6Ω6\Omega so that the combination has a resistance of 9Ω9\Omega, we can connect them in parallel. This is because when resistors are connected in parallel, the total resistance is less than any of the individual resistances. The formula for the total resistance of resistors connected in parallel is: rac{1}{R_{total}} = rac{1}{R_1} + rac{1}{R_2} + rac{1}{R_3} where RtotalR_{total} is the total resistance and R1R_1, R2R_2, and R3R_3 are the individual resistances. In this case, we have: rac{1}{R_{total}} = rac{1}{6} + rac{1}{6} + rac{1}{6} = rac{3}{6} = rac{1}{2} Therefore, the total resistance is 2Ω2\Omega. However, we want the total resistance to be 9Ω9\Omega, so we need to adjust the connection. One way to do this is to connect two of the resistors in series and then connect the third resistor in parallel with the series combination. The formula for the total resistance of resistors connected in series is: Rtotal=R1+R2+R3R_{total} = R_1 + R_2 + R_3 In this case, we have: Rtotal=6+6=12ΩR_{total} = 6 + 6 = 12\Omega Now, we can connect the third resistor in parallel with the series combination: rac{1}{R_{total}} = rac{1}{12} + rac{1}{6} = rac{3}{12} = rac{1}{4} Therefore, the total resistance is 4Ω4\Omega. However, we still need to adjust the connection to get a total resistance of 9Ω9\Omega. One way to do this is to add another resistor in series with the parallel combination. Let's call this resistor R4R_4. The formula for the total resistance of resistors connected in series is: Rtotal=R1+R2+R3+R4R_{total} = R_1 + R_2 + R_3 + R_4 In this case, we have: Rtotal=4+R4R_{total} = 4 + R_4 We want the total resistance to be 9Ω9\Omega, so we can set up the equation: 4+R4=94 + R_4 = 9 Solving for R4R_4, we get: R4=5ΩR_4 = 5\Omega Therefore, we need to add a resistor of 5Ω5\Omega in series with the parallel combination to get a total resistance of 9Ω9\Omega.

resistorsseriesparalleltotal resistance

Marking Scheme

  • 1Connect two of the resistors in series.
  • 2Connect the third resistor in parallel with the series combination.
  • 3Add another resistor in series with the parallel combination to get a total resistance of 9Ω9\Omega.

Hint

Use the formulas for the total resistance of resistors connected in series and parallel to solve this problem.

Quick Oral Answer

To connect three resistors each of resistance 6Ω6\Omega so that the combination has a resistance of 9Ω9\Omega, we can connect them in parallel. However, we need to adjust the connection to get a total resistance of 9Ω9\Omega. One way to do this is to connect two of the resistors in series and then connect the third resistor in parallel with the series combination. We can then add another resistor in series with the parallel combination to get a total resistance of 9Ω9\Omega.

Analysis & Explanation

The key to solving this problem is to understand how to connect resistors in series and parallel to achieve a desired total resistance. By connecting two of the resistors in series and then connecting the third resistor in parallel with the series combination, we can get a total resistance of 4Ω4\Omega. However, we still need to adjust the connection to get a total resistance of 9Ω9\Omega. By adding another resistor in series with the parallel combination, we can achieve the desired total resistance.

Common Mistakes

  1. 1Connecting all three resistors in series.
  2. 2Connecting all three resistors in parallel.

Interesting Facts

The total resistance of resistors connected in series is always greater than any of the individual resistances.

The total resistance of resistors connected in parallel is always less than any of the individual resistances.

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Frequently Asked Questions

How many marks does this question carry in CBSE Class 10 Science 2024?

This question carries 2 marks in the CBSE Class 10 Science 2024 examination.

Which chapter does this question come from in Science?

This question is from the chapter "Electricity" in the CBSE Class 10 Science syllabus.

What topic does this question cover in Science?

This question covers the topic "Electric Circuits" from CBSE Class 10 Science.

What type of question is this in the CBSE Class 10 Science 2024 paper?

This is a Very Short Answer question from Section B in the CBSE Class 10 Science 2024 paper.