Communication System — Physics STD 12 Science — Question

The nature of binding for a crystal with alternate and evenly spaced positive and negative ions is

(a) Covalent

(b) Metallic

(c) Dipolar

(d) Ionic

N-type semiconductors will be obtained, when germanium is doped with

(a) Phosphorus

(b) Aluminium

(c) Arsenic

(d) Both (a) or (c)

Mark out the correct options.

A charged particle moves in a magnetic field. The only force influencing the particle is the force caused by the magnetic field.
During the particle's movement in the magnetic field, what will NOT change?

The net resistance of a voltmeter should be large to ensure that

(a) It does not get overheated

(b) It does not draw excessive current

(c) It can measure large potential difference

(d)  It does not appreciably change the potential difference to be measured

Which one of the following statements is not correct

(a) A diode does not obey Ohm's law

(b) A PN junction diode symbol shows an arrow identifying the direction of current (forward) flow

(c) An ideal diode is an open switch

(d) An ideal diode is an ideal one way conductor

How much energy in kilowatt hour is consumed in operating ten 50 watt bulbs for 10 hours per day in a month (30 days).

(a) 1500

(b) 5,000

(c) 15

(d) 150

Which of the following graphs shows the variation of magnetic induction B with distance r from a long wire carrying current

(a)

(b)

(c)

(d)

The energy of hydrogen atom in its ground state is – 13.6 eV. The energy of the level corresponding  to the quantum number n is equal 5 is

(a) – 5.40 eV

(b) – 2.72 eV

(c) – 0.85 eV

(d) – 0.54 eV

The earth's magnetic induction at a certain point is 7 × .  This is to be annulled by the magnetic induction at the centre of a circular conducting loop of radius 5 cm. The required current in the loop is

(a) 0.56 A

(b) 5.6 A

(c) 0.28 A

(d) 2.8 A