MCQEasyJEE 2024Significant Figures & Error Analysis

JEE Physics 2024 Question with Solution

The resistance R=VIR = \frac{V}{I} where V=(200±5)VV = (200\pm 5)\,\text{V} and I=(20±0.2)AI = (20\pm 0.2)\,\text{A}. The percentage error in the measurement of RR is:

  • A

    3.5%3.5\%

  • B

    7%7\%

  • C

    3%3\%

  • D

    5.5%5.5\%

Answer

Correct answer:A

Step-by-step solution

the solution unavailable

Given: R=VIR = \frac{V}{I}, V=(200±5)VV = (200\pm 5)\,\text{V}, I=(20±0.2)AI = (20\pm 0.2)\,\text{A}.

Find: Percentage error in RR.

Working could not be extracted from the solution. Using error propagation for division, the fractional errors add:

ΔRR=ΔVV+ΔII\frac{\Delta R}{R} = \frac{\Delta V}{V} + \frac{\Delta I}{I}

So,

ΔRR×100=(5200+0.220)×100\frac{\Delta R}{R}\times 100 = \left(\frac{5}{200} + \frac{0.2}{20}\right)\times 100 =(0.025+0.01)×100=3.5%= (0.025 + 0.01)\times 100 = 3.5\%

Therefore, the correct option is A.

Common mistakes

  • Adding absolute errors 55 and 0.20.2 directly is incorrect because percentage or fractional errors must be combined for quantities related by division. First convert each uncertainty to fractional form, then add them.

  • Using subtraction of errors for VI\frac{V}{I} is wrong. Although the variables are divided, the maximum fractional errors always add when propagating error in a quotient.

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