Q12 of 805 Page 1

A point charge + Q is placed at the centre O of an uncharged hollow spherical conductor of inner radius ‘a’ and outer radius ‘b’. Find the following:

(a) The magnitude and sign of the charge induced on the inner and outer surface of the conducting shell.


(b) The magnitude of electric field vector at a distance (i) r = , and (ii) r = 2b, from the centre of the shell.


(a) Charge placed at the centre of the shell is + Q. So a charge of magnitude -Q will be induced on the inner surface of the sphere. The charge on the outer sphere will be + Q.


(b) By applying Gauss law


(1) Field at an inside point


At r = a/2



= N/C


(2) Field at an outside point


At r = 2b



= N/C


More from this chapter

All 805 →
10

Give reason, why high frequency carrier waves are needed for effective transmission of information signals.

OR


What is the range of frequencies used for T.V. transmission? State two factors by which the range of TV signals can be increased.

 11

(a) How many electrons must be added to one plate and removed from the other so as to store 25.0 J of energy in a 5.0 nF parallel plate capacitor?

(b) How would you modify this capacitor so that it can store 50.0 J of energy without changing the charge on its plates?

 13

The following table gives the length of three copper wires, their diameters, and the applied potential difference across their ends. Arrange the wires in increasing order according to the following:

(a) The magnitude of the electric field within them,


(b) The drift speed of electrons through them, and


(c) The current density within them.


 14

A multirange voltmeter can be constructed by using a galvanometer circuit as shown in the figure. We want to construct a voltmeter that can measure 2V, 20V and 200V using a galvanometer of resistance 10Ω and that produces maximum deflection for a current of 1 mA. Find the value of R1, R2 and R3 that have to be used.