Electromagnetic Waves — Physics STD 12 Science — Question

Consider telecommunication through optical fibres.  Which of the following statements is not true

(a) Optical fibres may have homogeneous core with a suitable cladding

(b) Optical fibres can be of graded refractive index

(c) Optical fibres are subject to electromagnetic interference from outside

(d) Optical fibres have extremely low transmission loss

The magnetic field in a coil of 100 turns and 40 square cm area is increased from 1 Tesla to 6 Tesla in 2 second. The magnetic field is perpendicular to the coil. The e.m.f. generated in it is

(a)

(b) 1.2 V

(c) 1.0 V

(d)

The total work done on a particle is equal to the change in its kinetic energy:

1. Always.
2. Only if the forces acting on it are conservative.
3. Only if gravitational force alone acts on it.
4. Only if elastic force alone acts on it.

An ammeter of 5 ohm resistance can read 5 mA. If it is to be used to read 100 volts, how much resistance is to be connected in series

(a) 19.9995 Ω

(b) 199.995 Ω

(c) 1999.95 Ω

(d) 19995 Ω

The SI unit of dipole moment is:

An electron is ejected from the surface of a long, thick straight conductor carrying a current, initially in a direction perpendicular to the conductor. The electron will:

The negative Zn pole of a Daniel cell, sending a constant current through a circuit, decreases in mass by 0.13g in 30 minutes. If the electrochemical equivalent of Zn and Cu are 32.5 and 31.5 respectively, the increase in the mass of the positive Cu pole in this time is

(a) 0.242 g

(b) 0.190 g

(c) 0.141 g

(d) 0.126 g

In L-R circuit, for the case of increasing current, the magnitude of current can be calculated by using the formula

(a)

(b)

(c)

(d)

The unit of focal power of a lens is

(a) Watt

(b) Horse power

(c) Dioptre

(d) Lux