The work done by a conservative force in moving a particle along a closed path is:
A. Zero
B. Negative
C. Depends on path
D. Positive
Answer: Option A
Solution (By JKSSB Mock Tests)
Conservative forces (gravity, spring, electrostatic) have path-independent work; work done over any closed loop is zero. This defines conservative forces and enables potential energy definition. Non-conservative forces (friction) have non-zero closed-path work. Memory aid: 'Conservative force: ∮F·dr = 0; enables energy conservation'. This mechanics concept is frequently tested in competitive exams. Always link conservative forces to potential energy and mechanical energy conservation; this is foundational for advanced physics problem-solving.
Explanation:
Electrical energy (E) = Power (P) × Time (t). Power = 60 W = 0.06 kW. Time per day = 5 hours. Total time in 30 days = 5 × 30 = 150 hours. Energy = 0.06 kW × 150 h = 9 kWh (or 9 units of electricity). One kWh is the commercial unit of energy.
Explanation:
Watt is unit of power (J/s). Kilowatt-hour is energy (power × time). Joule is SI unit of energy. Electron volt is energy unit (1.6×10⁻¹⁹ J). Remember: power = energy/time. So watt is not energy.
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