Dimensionless quantities: angle (radian = arc/radius), strain (ΔL/L), refractive index (ratio of speeds). All have [M⁰L⁰T⁰]. Memory aid: 'Ratios of same dimensions ⇒ dimensionless'. Dimensional analysis question frequently tested in competitive exams to identify dimensionless physical quantities.
Explanation:
Centripetal force acts towards centre, necessary for circular motion. Centrifugal is pseudo-force in rotating frame. In uniform circular motion, centripetal force = mv²/r.
Explanation:
Fuse is a safety device: thin wire melts when current exceeds safe limit due to short circuit or overload, breaking circuit. Prevents fire and appliance damage. Based on heating effect. MCB is modern alternative.
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