Q. The half-life of a radioactive substance is 10 days. After 30 days, the remaining fraction is:

  • (A) 1/2
  • (B) 1/4
  • (C) 1/8
  • (D) 1/16
๐Ÿ“ Notes
โœ… Correct Answer: (C) 1/8
Explanation: 30 days correspond to 3 half-lives. Remaining fraction = (1/2)^3 = 1/8.

Q. The power factor of a purely resistive AC circuit is:

  • (A) 0
  • (B) 0.5
  • (C) 1
  • (D) Infinity
๐Ÿ“ Notes
โœ… Correct Answer: (C) 1
Explanation: In a purely resistive circuit, voltage and current are in phase, so power factor cosφ = 1.

Q. The moment of inertia depends upon:

  • (A) Only mass
  • (B) Only shape
  • (C) Mass and distribution of mass about the axis
  • (D) Only angular velocity
๐Ÿ“ Notes
โœ… Correct Answer: (C) Mass and distribution of mass about the axis
Explanation: Moment of inertia depends on both the mass and how the mass is distributed with respect to the axis of rotation.

Q. For an ideal gas, PV = nRT. Here R is called:

  • (A) Gas coefficient
  • (B) Universal gas constant
  • (C) Specific heat
  • (D) Thermal constant
๐Ÿ“ Notes
โœ… Correct Answer: (B) Universal gas constant
Explanation: R is the universal gas constant with value 8.314 J mol^-1 K^-1.

Q. The de Broglie wavelength is inversely proportional to:

  • (A) Mass
  • (B) Velocity
  • (C) Momentum
  • (D) Energy
๐Ÿ“ Notes
โœ… Correct Answer: (C) Momentum
Explanation: According to de Broglie hypothesis, λ = h/p, where p is momentum. Hence wavelength is inversely proportional to momentum.

Q. The SI unit of power is:

  • (A) Joule
  • (B) Newton
  • (C) Watt
  • (D) Pascal
๐Ÿ“ Notes
โœ… Correct Answer: (C) Watt
Explanation: Power is the rate of doing work. Its SI unit is Watt (W), where 1 W = 1 J/s.

Q. Which of the following is the unit of electric potential?

  • (A) Ohm
  • (B) Ampere
  • (C) Volt
  • (D) Coulomb
๐Ÿ“ Notes
โœ… Correct Answer: (C) Volt
Explanation: Electric potential difference is measured in volts (V).

Q. The acceleration due to gravity at the center of Earth is:

  • (A) 9.8 m/s²
  • (B) 4.9 m/s²
  • (C) Infinite
  • (D) Zero
๐Ÿ“ Notes
โœ… Correct Answer: (D) Zero
Explanation: At the center of Earth, gravitational pulls from all directions cancel each other, so g = 0.

Q. A projectile is thrown at an angle of 45°. The ratio of its maximum height to horizontal range is:

  • (A) 1 : 2
  • (B) 1 : 4
  • (C) 1 : 1
  • (D) 2 : 1
๐Ÿ“ Notes
โœ… Correct Answer: (B) 1 : 4
Explanation: For θ = 45°, H = u²/4g and R = u²/g. Therefore, H:R = 1:4.

Q. The work done in moving a charge in an equipotential surface is:

  • (A) Maximum
  • (B) Minimum
  • (C) Zero
  • (D) Infinite
๐Ÿ“ Notes
โœ… Correct Answer: (C) Zero
Explanation: Potential difference between any two points on an equipotential surface is zero, so work done is also zero.

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