Nuclei — Physics STD 12 Science — Question

A region surrounding a stationary electric dipoles has(a) Magnetic field only(b) Electric field only(c) Both electric and magnetic fields(d) No electric and magnetic fields

Unit of e.m.f. of a cell is:

A freshly prepared radioactive sample of half- life 1 hour emits radiations that are 128 times as intense as the permissible safe limit. The minimum time after which this sample can be safely used is(a) 14 hours(b) 7 hours(c) 128 hours(d) 256 hours

Two wires of the same material and equal length are joined in parallel combination.  If one of them has half the thickness of the other and the thinner wire has a resistance of 8 ohms, the resistance of the combination is equal to

The power of a convex lens is :

Four wires of equal length and of resistances 10 ohms each are connected in the form of a square. The equivalent resistance between two opposite corners of the square is(a) 10 ohm(b) 40 ohm(c) 20 ohm(d) 10/4 ohm

Polarisation of light establishes:

Two negative charges are kept at a certain distance in the air medium. What will happen if a dielectric slab is inserted between them?