Electric motor works on principle of: MCQ with Answer and Explanation

Explanation:
Work (W) = F × d × cos(θ). In scenario A, displacement (d) is zero. In scenario B, the applied force (upward) is perpendicular to the displacement (horizontal), so cos(90°) = 0. In scenario C, the centripetal force (gravity) is perpendicular to the satellite's instantaneous direction of motion, so work done is zero. All cases yield zero work.

Explanation:
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:
Copper wire obeys Ohm's law (V ∝ I) at constant temperature. Diode, transistor are non-ohmic (non-linear). Electrolytes can be non-linear. Metals are ohmic.