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NEET PHYSICSEasy

Which relation is wrong?

A

1 Calorie = 4.18 Joules

B

1 A˚=10−10\mathring{A} = 10^{-10} m

C

1 MeV = 1.6×10−131.6 \times 10^{-13} Joules

D

1 Newton = 10−510^{-5} Dynes

Step-by-Step Solution

  1. Analyze Option A: 1 calorie is defined as the heat energy required to raise the temperature of 1 g of water by 1∘1^{\circ}C. The mechanical equivalent of heat is approximately 4.184.18 J (or 4.1864.186 J). Thus, 1 Cal≈4.18 J1 \text{ Cal} \approx 4.18 \text{ J}. This relation is correct .
  2. Analyze Option B: The Angstrom (A˚\mathring{A}) is a unit of length used in atomic physics. 1A˚=10−10 m1 \mathring{A} = 10^{-10} \text{ m}. This relation is correct .
  3. Analyze Option C: 1 electron volt (eV) is 1.6×10−191.6 \times 10^{-19} J. Therefore, 1 Mega electron volt (MeV) = 106 eV=106×(1.6×10−19 J)=1.6×10−13 J10^6 \text{ eV} = 10^6 \times (1.6 \times 10^{-19} \text{ J}) = 1.6 \times 10^{-13} \text{ J}. This relation is correct .
  4. Analyze Option D: The Newton (N) is the SI unit of force, and the Dyne is the CGS unit of force.
  • 1 N=1 kg m s−2=(1000 g)(100 cm) s−2=105 g cm s−2=105 Dynes1 \text{ N} = 1 \text{ kg m s}^{-2} = (1000 \text{ g})(100 \text{ cm}) \text{ s}^{-2} = 10^5 \text{ g cm s}^{-2} = 10^5 \text{ Dynes}.
  • The option states 1 N=10−5 Dynes1 \text{ N} = 10^{-5} \text{ Dynes}, which is incorrect. The correct relation is 1 Dyne=10−5 N1 \text{ Dyne} = 10^{-5} \text{ N} .
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