Atoms — Physics STD 12 Science — Question

If a copper rod carries a direct current, the magnetic field associated with the current will be:

The combined capacity of the parallel combination of two capacitors is four times their combined capacity when connected in series. This means that

(a) Their capacities are equal	(b) Their capacities are 1 μF and 2 μF
(c) Their capacities are 0.5 μF  and 1 μF	(d) Their capacities are infinite

A person cannot see objects clearly beyond 2.0 m. The power of lens required to correct his vision will be

(a) + 2.0 D

(b) – 1.0 D

(c) + 1.0 D

(d) – 0.5 D

Calculate the amount of charge flowing in 2 minutes in a wire of resistance 10 W when a potential difference of 20 V is applied between its ends

(a) 120 C

(b) 240 C

(c) 20 C

(d) 4 C

If a dielectric introduced between the plates of a parallel plate condenser, then which of the following is possible:

A cell of e.m.f. E is connected with an external resistance R, then p.d. across cell is V. The internal resistance of cell will be

(a)

(b)

(c)

(d)

A triangular prism of glass is shown in the figure. A ray incident normally to one face is totally reflected, if θ = 45° . The index of refraction of glass is

(a) Less than 1.41

(b) Equal to 1.41

(c) Greater than 1.41

(d) None of the above

The contribution in the total current flowing through a semiconductor due to electrons and holes are   and   respectively. If the drift velocity of electrons is   times that of holes at this temperature, then the ratio of concentration of electrons and holes is

(a) 6 : 5

(b) 5 : 6

(c) 3 : 2

(d) 2 : 3

A point charge is kept at the centre of a metallic insulated spherical shell. Then

(a) Electric field out side the sphere is zero	(b) Electric field inside the sphere is zero
(c) Net induced charge on the sphere is zero	(d) Electric potential inside the sphere is zero

Which type of current is flowing through a circuit?