Electromagnetic Induction — Physics STD 12 Science — Question

Answer the following questions:
The charged currents in the outer conducting regions of the earth’s core are thought to be responsible for earth’s magnetism. What might be the ‘battery’ (i.e., the source of energy) to sustain these currents?

Why are convex mirrors used in making rear side view mirrors in cars?

A point charge +Q is placed at point O as shown in the figure. Is the potential difference V_A – V_B positive, negative or zero?

A concave lens of refractive index 1.5 is immersed in a medium of refractive index 1.65. What is the nature of the lens?

A bar magnet falls from a height ‘h’ through a metal ring. Will its acceleration be equal to g? Give reason for your answer.

The increase in the speed of a car is proportional to the additional petrol put into the engine. Is it possible to accelerate a car without putting more petrol or less petrol into the engine?

Water flows at a speed of 6cm/s through a tube of radius 1cm. Coefficient of viscosity of water at room termperature is 0.01 poise. Calculate the Reynolds number. Is it a steady flow?

If temperature of an electric conductor (i) increases (ii) decreases, how the relaxation time of electrons changes in it?

Specific resistance of copper, silver and constantan are 1.18 × 10^–6, 1 × 10^–6, 45 × 10⁶ ohm cm respectively. Which is the best electrical conductor and why?