Free Physical Quantities and Units MCQs with Answers

• A. 1
• B. 2
• C. 3
• D. 4

Explanation: Given,Area= circumference πr² = 2πrCutting π and r on both sidesr = 2

• A. bar
• B. atm
• C. Pascal
• D. erg

Explanation: Fact. According to the formula Pressure=Force/Area 1 N/m2 = 1 Pascal

• A. 1/24 x 1/60 x 1/60 of a mean solar day
• B. The second as defined by the electronic digital watch
• C. Duration of 9,192,631,770 vibrations of a cesium-133 atom
• D. Minute

Explanation: The SI unit of time is the second, symbolized as 's'. The modern definition is based on the cesium-133 atom's vibrations: specifically, 9,192,631,770 vibrations. This provides a highly precise standard. Option A refers to an outdated definition based on the Earth's rotation, which is variable. Option B is incorrect because digital watches use the standard definition rather than define it. Option D is incorrect because a minute is a derivative unit, not the base SI unit.

• A. 1.7588×10^19 Coulomb
• B. 1.6022×10^-19 Coulomb
• C. 1.2057×10^19 Coulomb
• D. 0.6022×10^19 Coulomb

Explanation: 1.6022×10^-19 Coulomb: This option is correct. The charge of an electron is approximately -1.6022×10^-19 Coulomb.

• A. Weber
• B. Weber meter^-2
• C. Tesla
• D. Henry

Explanation: Henry is the SI unit of inductance, symbolized by the letter H.

• A. 4/3 π radian
• B. 4/3 π steradian
• C. 4 π radian
• D. 4 π streradian

Explanation: One steradian is the solid angle of a sphere subtended by a portion of the surface whose area is equal to the square of the sphere's radius. The complete surface area of a sphere= 4πr² so the total solid angle about a point = 4πr²/r² = 4π steradian The steradian is the unit of solid angles. It is used in 3D geometry. Whereas the radian is used in planar geometry so options A and C are ruled out as we are dealing with a 3D cone here. (The mention of surface area in the question implies that 3D geometry is involved)

• A. 50 mA
• B. 50 µA
• C. 500 mA
• D. 500 µA

Explanation: The current of 0.05 A can be expressed as 50 mA because 'milli' means one thousandth, making 0.05 A equivalent to 50 milliamperes. Option A is correct. Option B (50 µA) and Option D (500 µA) are incorrect because microamperes are much smaller than milliamperes. Option C (500 mA) is incorrect because it represents a larger current than 0.05 A.

• A. 104
• B. 109
• C. 10-6
• D. 1012

Explanation: Tera donates multiplication by one trillion or 10¹².OPTION A: The prefix "myria" OPTION B: The prefix "Giga" stands for 10^9.OPTION C: The prefix "micro" stands for 10^-6.

• A. Mass, acceleration, temperature, kinetic energy
• B. Mass, volume, electrical potential, kinetic energy
• C. Acceleration, temperature, volume, electric charge
• D. Momentum, electric intensity, density, magnetic flux.

Explanation: A scalar quantity contains only magnitude and no direction, making options B the correct answer. Mass, volume, and electrical potential are all examples of scalar quantities as they can be fully described by their magnitude alone. Kinetic energy is also a scalar quantity due to the mathematical relationship between mass and velocity. Options A, C, and D include vector quantities, such as acceleration, momentum, and electric intensity, which have both magnitude and direction, making them incorrect choices for this question.

• A. Kg m s-1
• B. Kg m-1 s-2
• C. Kg m2 s-2
• D. Kg m-2 s-1

Explanation: Pressure is calculated as force per unit area. In this case, the correct unit of pressure is Kg m-1 s-2. This unit is derived from the formula P = F/A, where force is measured in Kg m s-2 and area in m2. This simplifies to Kg m-1 s-2, which is the unit of pressure.Option A is incorrect as it represents the unit of momentum, not pressure. Option C is also incorrect as it represents the unit of energy or work. Option D is not the unit of pressure either.