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

A man is sitting on a rotating stool with his arms outstretched. If suddenly he folds his arm the angular velocity of the man would:

• increase

• decrease

• become zero

• remain constant

For a particle revolving in a circular path, the acceleration of the particle is:

• along the tangent

• along the radius

• zero

• along the circumference of the circle

A circus performer of mass M is walking along a wire as shown in the figure given above. The tension T in the wire is : (g = acceleration due to gravity)

• approximately Mg

• less than Mg

• more than Ma

• depends on whether the performer stands on one or two feet

A heavy ball is suspended as shown in the figure given above. A quick jerk on the lower string will break that string but a slow pull on the lower string will break the upper string. The first result occurs because:

• the force is too small to move the ball

• air friction holds the ball back

• of action and reaction

• the ball has inertia

The visible light has a wavelength range from about 380 nm (violet) to 780 nm (red). If an exciting object emits light with a wavelength of 15 nm, to which one of the following ranges does it belong?

• X-ray

• Gamma ray

• Infrared

• Ultraviolet