Sound moves with higher velocity if:

• pressure of the medium is decreased

• temperature of the medium is increased

• the humidity of the medium is increased

• both B and C above

Which one of the following is the correct angle between the incident and reflected rays when a ray of light incident normally on a plane mirror?

• 180°

• 90°

• 45°

• 0°

Which one of the following four glass lenses is a diverging lens?

The magnetism of a bar magnet can be destroyed if it is:

1. kept in the magnetic meridian
2. placed in a direction opposite that of the Earth's horizontal intensity.
3. heated to a temperature known as Curie temperature

Select the correct answer using the code given below:

• 1 and 3 only

• 2 only

• 2 and 3 only

• 1,2 and 3

The capacity of a parallel plate condenser can be doubled by:

1. doubling the areas of the plates
2. doubling the distance of separation between the plates
3. reducing the distance of separation between the plates to half the original separation
4. doubling both the areas of the plates and the distance of separation between the plates

Select the correct answer using the code given below:

• 1 and 4

• 1 and 3

• 3 only

• 2 and 3

If two conducting spheres are separately charged and then brought in contact:

• the total energy ofthe two spheres is conserved

• the total charge on the spheres is conserved

• both the total energy and charge are conserved

• the final potential is always the mean of the original potential of the two spheres

Two pieces of metallic wire having an equal length and equal volume placed in the air have different resistances. The two wires must:

• have different cross-sections

• have different temperatures

• be of different materials

• be of same density

If a heater coil is cut into two equal parts and only one part is used in the heater, the heat generated will be :

• doubled

• four times

• one-fourth

• halved

The direction of the magnetic field at a point due to an infinitely long wire carrying current is:

• parallel to the current

• antiparallel to the current

• along the perpendicular drawn from a point on the wire

• perpendicular to the plane containing the conductor and the point

A hollow metal ball-carrying an electric charge produces no electric field at points:

• outside the sphere

• on its surface

• inside the sphere

• only at the centre