CBSE Guess Forums

pls help me with these qtns.... im finding it a bit difficult
.... hav a test 2moro....
1. An electrical element X, when connected to an alternating voltage source, has the current through it leading the
voltage by radii. Identify X and write an expression for its reactance

2. A light bulb (B) and iron cored inductor is connected to a DC battery through a switch (S).
(i) What will one observe when switch (S) is closed?
(ii) How will the glow of the bulb change when the battery is replaced by an ac source of rms voltage equal to the
voltage of DC battery? Justify your answer in each case.

3. When a circuit element ‘X’ is connected across an a.c. source, a current of A flows through it and this current
is in phase with the applied voltage. When another element ‘Y’ is connected across the same a.c. source, the same
current flows in the cricuit but it leads the voltage by radians.
(i) Name the circuit elements X and Y.
(ii) Find the current that flows in the circuit when the series combination of X and Y is connected across the same
a.c. voltage.
(iii) Plot a graph showing variation of the net impedance of this series combination of X and Y as a function of the
angular frequency of the applied voltage.

TNX A LOT