Nuclei — Physics STD 12 Science — Question

Consider the situation of the previous problem. The directions of the magnetic field due to the dipole are opposite at:

The temperature coefficient of resistance of a semiconductor

(a) Is always positive	(b) Is always negative
(c) Is zero	(d) May be positive or negative or zero

An electric current passes through a long straight wire. At a distance 5 cm from the wire, The magnetic field is B. The field at 20 cm  from the wire would be

(a)

(b)

(c)

(d)

Two ions having masses in the ratio 1 : 1 and charges 1 : 2 are projected into uniform magnetic field perpendicular to the field with speeds in the ratio 2 : 3. The ratio of the radii of circular paths along which the two particles move is

(a) 4 : 3

(b) 2 : 3

(c) 3 : 1

(d) 1 : 4

A cube of a metal is given a positive charge Q. For the above system, which of the following statements is true

(a) Electric potential at the surface of the cube is zero

(b) Electric potential within the cube is zero

(c) Electric field is normal to the surface of the cube

(d) Electric field varies within the cube

In Boolean algebra, Y = A + B implies that:

4 bulbs marked 40 W, 250 V are connected in series with 250 V mains. The total power is

(a) 10 W

(b) 40 W

(c) 320 W

(d) 160 W

Five balls numbered 1 to 5 are suspended using separate threads. Pairs (1, 2), (2, 4) and (4, 1) show electrostatic attraction, while pair (2, 3) and (4, 5) show repulsion. Therefore ball 1 must be

(a) Positively charged

(b) Negatively charged

(c) Neutral

(d) Made of metal

Let F_pp, F_pn and F_nn denote the magnitudes of the net force by a proton on a proton, by a proton on a neutron and by a neutron on a neutron respectively. Neglect gravitational force. When the separation is 1fm:

In an electrolyte 3.2   bivalent positive ions  drift to the right per second while 3.6   monovalent negative ions drift to the left per second. Then the current is

(a) 1.6 amp to the left

(b) 1.6 amp to the right

(c) 0.45 amp to the right

(d) 0.45 amp to the left