Electrostatics — Physics STD 12 Science — Question

A positively charged particle moving in east direction enters a region of uniform magnetic field directed vertically upwards. What will be the path of the particle?

Assertion  :   The lightening conductor at the top of high building has sharp pointed ends.
Reason     : The surface density of charge at sharp points is very high resulting in setting up of electric wind.(a) If both assertion and reason are true and the reason is the correct explanation of the assertion.(b) If both assertion and reason are true but reason is not the correct explanation of the assertion.(c) If assertion is true but reason is false.(d) If the assertion and reason both are false.

The impurity atoms with which pure silicon may be doped to make it a p-type semiconductor are those of:

1. Phosphorus.
2. Boron.
3. Antimony.
4. Aluminium.

There is no couple acting when two bar magnets are placed coaxially separated by a distance because(a) There are no forces on the poles(b) The forces are parallel and their lines of action do not coincide(c) The forces are perpendicular to each other(d) The forces act along the same line

Cylindrical lenses are used to correct the eye defect called :

A tank is filled with benzene to a height of 120 mm. The apparent depth of a needle lying at a bottom of the tank is measured by a microscope to be 80 mm.  The refractive index of benzene is(a) 1.5 (b) 2.5(c) 3.5(d) 4.5

Energy in the sun is generated mainly by(a) Fusion of radioactive material(b) Fission of helium atoms(c) Chemical reaction(d) Fusion of hydrogen atoms

A stream of electrons is projected horizontally to the right. A straight conductor carrying a current is supported parallel to electron stream and above it. If the current in the conductor is from left to right then what will be the effect on electron stream  (a) The electron stream will be pulled upward(b) The electron stream will be pulled downward(c) The electron stream will be retarted(d) The electron beam will be speeded up towards the right