Magnetism And Matter — Physics STD 12 Science — Question

Samples of two radioactive nuclides A and B are taken. λA and λB are the disintegration constants of A and B respectively. In which of the following cases, the two samples can simultaneously have the same decay rate at any time?

A galvanometer, having a resistance of 50 W gives a full scale deflection for a current of 0.05 A. The length in meter of a resistance wire of area of cross-section 2.97 X 10^–2 cm² that can be used to convert the galvanometer into an ammeter which can read a maximum of 5 A current is (Specific resistance of the wire = 5   Wm)

(a) 9

(b) 6

(c) 3

(d) 1.5

Two metal spheres of capacitance   and  carry some charges. They are put in contact and then separated. The final charges  and   on them will satisfy

(a)

(b)

(c)

(d)

The equivalent capacitance in the circuit between A and B will be

(a) 1 μF

(b) 2 μF

(c) 3 μF

(d)

The true statement is

(a) The order of colours in the primary and the secondary rainbows is the same

(b) The intensity of colours in the primary and the secondary rainbows is the same

(c) The intensity of light in the primary rainbow is greater and the order of colours is the same than the secondary rainbow

(d) The intensity of light for different colours in primary rainbow is greater and the order of colours is reverse than the secondary rainbow

Which of the following statement is correct in accordance with Kirchhoff's second law?

The electric field intensity produced by the radiations coming from 100W bulb at a 3 m distance is E. The electric field intensity produced by the radiations coming from 50W bulb at the same distance is:

A positive charge Q is uniformly distributed along a circular ring of radius R.A. small test charge q is placed at the centre of the ring Fig. Then:

Two point charges 3 × 10^–6 C and 8 × 10^–6 C repel each other by a force of 6 × 10^–3 N. If each of them is given an additional charge – 6 × 10⁶ C, the force between them will be

(a) 2.4 × 10–3 N (attractive)	(b) 2.4 × 10–9 N (attractive)
(c) 1.5 × 10–3 N (repulsive)	(d) 1.5 × 10–3 N (attractive)

If a coil made of conducting wires is rotated between poles pieces of the permanent magnet. The motion will generate a current and this device is called

(a) An electric motor	(b) An electric generator
(c) An electromagnet	(d) All of above