Dual Nature of Radiation and Matter — Physics STD 12 Science — Question

An electron moving towards the east enters a magnetic field directed towards the north. The force on the electron will be directed

(a) Vertically upward	(b) Vertically downward
(c) Towards the west	(d) Towards the south

Sodium has body centred packing. If the distance between two nearest atoms is 3.7 Å, then its lattice parameter is

(a) 4.8 Å

(b) 4.3 Å

(c) 3.9 Å

(d) 3.3 Å

Two resistance wires on joining in parallel the resultant resistance is .  One of the wire breaks, the effective resistance is 2 ohms.  The resistance of the broken wire is

(a)

(b) 2 ohm

(c)

(d) 3 ohm

The distance between charges 5 ×   and -2.7   is 0.2 m. The distance at which a third charge should be placed in order that it will not experience any force along the line joining the two charges is

(a) 0.44 m

(b) 0.65 m

(c) 0.556 m

(d) 0.350 m

A semiconductor is doped with a donor impurity:

Ionic molecules are:

In the propagation of electromagnetic waves, the angle between the direction of propagation and plane of polarisation is

The i-V characteristic of a P-N junction diode is shown below. The approximate dynamic resistance of the P-N junction when a forward bias of 2volt is applied

(a)  1 W

(b)  0.25 W

(c)  0.5 W

(d)  5 W

A circular loop of radius 0.0157m carries a current of 2.0 amp. The magnetic field at the centre of the loop is (

(a) 1.57	(b) 8.0
(c) 2.5	(d)  3.14

If angular frequency of an A.C. source used in L-C-R circuit is increased, then inductive reactance __________ and capacitive reactance __________ .