Using the concept of force between two infinitely long parallel current carrying conductors, define one ampere of current. 

To which part of the electromagnetic spectrum does a wave of frequency 5  x 10¹⁹ Hz belong? 

Two equal balls having equal positive charge ‘q’ coulombs are suspended by two insulating strings of equal length. What would be the effect on the force when a plastic sheet is inserted between the two? 

The electric current flowing in a wire in the direction from B to A is decreasing. Find out the direction of the induced current in the metallic loop kept above the wire as shown. 

Why is the use of A.C. voltage preferred over D.C. voltage? Give two reasons. 

A parallel plate capacitor of capacitance C is charged to a potential V. It is then connected to another uncharged capacitor having the same capacitance. Find out the ratio of the energy stored in the combined system to that stored initially in the single capacitor.              

Considering the case of a parallel plate capacitor being charged, show how one is required to generalize Ampere’s circuital law to include the term due to displacement current.

A cell of emf ‘E’ and internal resistance ‘r’ is connected across a variable resistor ‘R’. Plot a graph showing variation of terminal voltage ‘V’ of the cell versus the current ‘I’. Using the plot, show how the emf of the cell and its internal resistance can be determined.

9.

Estimate the average drift speed of conduction electrons in a copper wire of cross-sectional area 1.0 x 10^–7 m² carrying a current of 1.5 A. Assume the density of conduction electrons to be 9 x 10²⁸ m^–3. 

Show diagrammatically the behaviour of magnetic field lines in the presence of (i) paramagnetic and (ii) diamagnetic substances. How does one explain this distinguishing feature?