The heating effect of electric current is utilised in MCQ with Answer and Explanation

Explanation:
Telescope (refracting/reflecting) makes distant objects appear nearer, magnified. Microscope for tiny near objects. Periscope uses mirrors to see over obstacles. Endoscope medical.

Explanation:
At 0°C ≈ 331 m/s, increases with temperature. At 20°C ≈ 343 m/s.

Explanation:
In uniform circular motion, speed remains constant but direction changes, so velocity (vector) changes. There is centripetal acceleration towards centre, so acceleration is not zero. Kinetic energy = ½mv², depends on speed, so remains constant. Thus, only speed is constant.