here's the best of the three:

 

A thin wheel can stay upright on its rim for a considerable length of time when rolled with a considerable velocity,while it falls from its upright position at the slightest disturbance,when stationary.explain.

(this question was asked in Roorkee exam)

 

ask me if you're having any doubt.

plz do rate the questions if useful!!!!!!!

here are previous years' 1 mark questions from electrostatics:

 

1.what kind of charges are produced on each when a glass is rubbed with silk and an ebonite rod is rubbed with wool?(1990)

 

2.a 900 pF capacitor is charged by a 100 V battery.how much electrostatics energy is stored by the capacitor?(1990)

ans:4.5 * 10^-6

 

3.what are the factors on which capacitance of a parallel plate condenser depends?also give the formula.(1991)

 

4.show graphically the variation of charge 'q' with time 't' when a condenser is charged.(1990)

 

5.what is a conservative field?(1990)