MODEL PAPER 7 — Physics STD 12 Science — Question

A moving charge produces:

A convex lens has a focal length f.  It is cut into two parts along the dotted line as shown in the figure.  The focal length of each part will be

(a)

(b) f

(c)

(d) 2f

Length of a magnetic iron wire is / and its magnetic moment is m. If on moulding it in the form of L, its all arms are of equal sizes, then magnetic moment of new shape will be:

A point charge +q  is placed at the centre of a cube of side L. The electric flux emerging from the cube is

(a)

(b) Zero

(c)

(d)

Identify the type of materials which develop electric currents in them, when an electric field is applied.

Liquids and gases never exhibit:

For a photoelectric cell the graph showing the variation of cut of voltage (V_o) with frequency (n) of incident light is best represented by

(a)

(b)

(c)

(d)

The velocity of light in a medium is half its velocity in air.  If ray of light emerges from such a medium into air, the angle of incidence, at which it will be totally internally reflected,   is

(a) 15o

(b) 30 o

(c) 45 o

(d) 60 o

The minimum energy required to excite a hydrogen atom from its ground state is

(a) 13.6 eV

(b) -13.6 eV

(c) 3.4 eV

(d) 10.2 eV

A flat circular disc has a charge +Q uniformly distributed on the disc. A charge +q is thrown with kinetic energy  E towards the disc along its normal axis. The charge q  will

(a) Hit the disc at the centre

(b) Return back along its path after touching the disc

(c) Return back along its path without touching the disc

(d) Any of the above three situations is possible depending on the magnitude of E