The force that keeps a body moving in a circular path is called
A. Centripetal force
B. Frictional force
C. Gravitational force
D. Centrifugal force
Answer: Option A
Solution (By JKSSB Mock Tests)
Centripetal force acts towards centre, necessary for circular motion. Centrifugal is pseudo-force in rotating frame. In uniform circular motion, centripetal force = mv²/r.
Which scientific instrument is used specifically for measuring very high temperatures, such as the surface temperature of the Sun or inside a furnace, from a distance?
Explanation:
A pyrometer is a non-contact thermometer used to measure high temperatures. It operates on the principle of thermal radiation (Stefan-Boltzmann law or Wien's law), measuring the intensity or spectrum of electromagnetic radiation emitted by the extremely hot object. A cryometer measures very low temperatures, and a calorimeter measures heat capacity.
Explanation:
Electric generators convert mechanical energy to electrical energy using electromagnetic induction: rotating a coil in magnetic field (or vice versa) induces EMF due to changing magnetic flux. This is Faraday's law application. Motors use the reverse principle (force on current-carrying conductor in field). Memory tip: 'Generator: motion ⇒ electricity (induction); Motor: electricity ⇒ motion (force)'. This application question tests understanding of device principles, common in competitive exams. Always distinguish generator (induction) from motor (Lorentz force) operation.
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