CBSE Delhi-Set-1-2012

On the equator,  and therefore the vertical component of earth's magnetic field is also zero.

Microwaves and UV radiations are a part of the electromagnetic spectrum. The physical quantity that remains same for both the radiations is their speed of propagation in vacuum, which is equal to  .

A biconvex lens will act as a plane sheet of glass if it is immersed in a liquid that has the same refractive index as the material of the biconvex lens. In this case, the focal length of the lens becomes infinite.

When an electric field is applied across a conductor, the electrons drift from lower to higher potential. The drift velocity of the electrons gets superimposed on the thermal velocity and as a result, each electron moves in the direction of the resultant of the drift and the thermal velocity. Thus, the resultant velocity and hence the direction of motion may be different for different electrons. The electrons may also collide with ions and may change its direction of motion.

According to the de Broglie hypothesis, a moving material particle (whether big or small) having a momentum ‘p’ will always have a wavelength  associated with it. Such waves are called matter waves or de Broglie waves having a wavelength,

As the temperature of a semi conductor is increased, the number density of electrons and that of holes increases. Therefore, its resistivity decreases with increasing temperature. The following curve shows the variation of resistivity with temperature for a typical semiconductor:

An electric conductor has a large number of free electrons. When the conductor is placed in an electric field, these electrons redistribute themselves on the surface of the conductor to make the field zero inside the conductor.

According to the Lenz’s Law, the current will be induced in a direction that opposes the increase of magnetic flux. The current I gives rise to a magnetic field in the outward direction through ring 1 & inward direction through ring 2.
Since the current (I) is steadily increasing in the wire, the induced current will be in the clockwise direction in ring 1 and in the anticlockwise direction in ring 2.

The red arrows show the direction of induced current in the rings.

Therefore, the electric field  shows an inverse square relationship whereas, the electric potential ‘V’ shows an inverse relationship with distance ‘r’ as shown below:

Since the susceptibility of the given material is negative, it is a diamagnetic material.
The properties of diamagnetic materials are as follows:
(i) A diamagnetic material placed inside a magnetic field gets feebly magnetized in a direction opposite to the direction of the magnetizing field.
(ii) Diamagnetic materials do not obey Curie’s law and their magnetic behavior does not change with a change in the temperature.