The gravitational force between two masses is F. If the distance between them is halved, the force becomes
A. F/2
B. 4F
C. F/4
D. 2F
Answer: Option B
Solution (By JKSSB Mock Tests)
Newton's law of gravitation: F ∝ 1/r². If distance r becomes r/2, new force F' ∝ 1/(r/2)² = 4/r² = 4F. So force quadruples. This inverse square law is fundamental for gravitational, electric, magnetic forces.
Explanation:
Michael Faraday discovered electromagnetic induction in 1831: changing magnetic field induces emf. Oersted discovered magnetic effect of current. Ampere gave laws of magnetic force between currents. Coulomb for electrostatics.
Explanation:
F = BIL sinθ. Maximum when θ = 90° (sin90°=1), so perpendicular. Parallel (θ=0°) force zero. This is the motor effect, used in electric motor.
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