Which of the following is a derived unit in SI system? MCQ with Answer and Explanation

Which of the following is a derived unit in SI system?
A. Newton
B. Mole
C. Kelvin
D. Ampere
Answer: Option A
Solution (By JKSSB Mock Tests)
Newton is a derived unit representing force, defined as kg·m/s². Kelvin (temperature), Ampere (current), and Mole (amount of substance) are fundamental SI units. Derived units are combinations of fundamental units through physical relationships. Newton comes from Newton's second law: F = ma. Memory aid: Remember the seven fundamental SI units: meter, kilogram, second, ampere, kelvin, mole, candela. All others like newton, joule, watt are derived. This distinction is essential for unit conversion questions in competitive exams.

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Practice More Physics Questions

Question #1
Heat required to raise 2 kg water from 20°C to 100°C: (c_water = 4200 J/kg·K)
A. 672 kJ
B. 168 kJ
C. 336 kJ
D. 840 kJ

Correct Answer: Option A


Explanation:
Q = mcΔT = 2×4200×(100-20) = 2×4200×80 = 672000 J = 672 kJ. Direct calorimetry formula application. Memory tip: 'Q = mcΔT; ΔT in Celsius or Kelvin same'. Basic numerical testing specific heat concept, frequently appearing in thermodynamics sections of competitive exams.

This question belongs to: Science Physics
Question #2
Alpha particles are
A. Helium nuclei
B. Electromagnetic waves
C. Electrons
D. Protons

Correct Answer: Option A


Explanation:
Alpha particles are helium nuclei (2 protons, 2 neutrons), charge +2e, mass 4 u. Beta particles are fast electrons (or positrons). Gamma rays are high-energy photons, no mass, no charge.

This question belongs to: Science Physics
Question #3
An electric bulb rated 220 V, 100 W is operated at 110 V. The power consumed is
A. 100 W
B. 25 W
C. 50 W
D. 12.5 W

Correct Answer: Option B


Explanation:
Resistance R = V²/P = 220²/100 = 484 Ω. At 110 V, P = V²/R = 110²/484 = 12100/484 = 25 W. Assuming resistance constant. Power reduces to quarter when voltage halved (P ∝ V² for fixed R).

This question belongs to: Science Physics