BSEB Bihar Board 12th Physics Important Questions Objective Type Part 2 are the best resource for students which helps in revision.

## Bihar Board 12th Physics Objective Important Questions Part 2

Question 1.

Magnetic field due to current carrying a wire at a distance from it is proportional to:

(i) r

(ii) \(\frac{1}{r}\)

(iii) \(\frac{1}{r^{2}}\)

(iv) r^{2}

Answer:

(ii) \(\frac{1}{r}\)

Question 2.

In for V ~ I graph for a conductor at temp. T_{1} & T_{2} is shown (T_{2} – T_{1}) is proportional to

(i) cos 2θ

(ii) sin 2θ

(iii) cot 2θ

(iv) tan 2θ

Answer:

(iii) cot 2θ

Question 3.

A galvanometer or voltmeter can be converted into an ammeter by connecting:

(i) high resistance in parallel

(ii) low resistance in parallel

(iii) high resistance in series

(iv) low resistance in series

Answer:

(ii) low resistance in parallel

Question 4.

A galvanometer or ammeter can be converted into a voltmeter by connecting:

(i) high resistance in parallel

(ii) high resistance in series

(iii) low resistance in parallel

(iv) low resistance in series

Answer:

(ii) high resistance in series

Question 5.

Shunt is used with a galvanometer to:

(i) increase its capacity sensitivity

(ii) increase its range

(iii) increase its resistance

(iv) protect from heavy current

Answer:

(iv) protect from heavy current

Question 6.

The rel^{n}. among the electric field (\(\vec{E}\)), current density \(\vec{J}\) and resistivity (ρ) is:

(i) \(\vec{E}=\rho \vec{J}\)

(ii) \(\vec{J}=\rho \vec{E}\)

(iii) \(\rho=\rho \vec{E} \cdot \vec{J}\)

(iv) None of these

Answer:

(i) \(\vec{E}=\rho \vec{J}\)

Question 7.

By using Shunt the range of an ammeter:

(i) is increased

(ii) is decreased

(iii) remains constant

(iv) None

Answer:

(i) is increased

Question 8.

Three equal resistance each of 3 Ohm resistance are connected in parallel their equivalent resistance is?

(i) 1 Ohm

(ii) 3 Ohm

(iii) 9 Ohm

(iv) None of these

Answer:

(i) 1 Ohm

Question 9.

The important law governing electromagnetic induction is called:

(i) Newton’s law

(ii) Ohm’s law

(iii) Faraday’s law

(iv) Ampere’s law

Answer:

(iii) Faraday’s law

Question 10.

If electron velocity is 2\(\hat{i}\) +3\(\hat{j}\) and it is subjected to magnetic field of 4\(\hat{k}\), there its:

(i) path will change

(ii) speed will change

(iii) both (i) and (ii)

(iv) None

Answer:

(i) path will change

Question 11.

Lenz’s is a consequence of the law of conservation of:

(i) charge

(ii) energy

(iii) mass

(iv) momentum

Answer:

(ii) energy

Question 12.

Induction coil is an instrument for generating:

(i) large current

(ii) high voltage

(iii) small current

(iv) small voltage

Answer:

(ii) high voltage

Question 13.

The motion of free electrons in between two successive collisions with the atoms/ions follows:

(i) a straight path

(ii) circular path

(iii) elliptical path

(iv) curved path.

Answer:

(iv) curved path

Question 14.

The working of an induction coil is based on the principle of:

(i) magnetic induction

(ii) electric induction

(iii) electromagnetic induction

(iv) None of these

Answer:

(iii) electromagnetic induction

Question 15.

The unit of self inductance is:

(i) Weber

(ii) Ohm

(iii) Henry

(iv) None

Answer:

(iii) Henry

Question 16.

Transformer is used to convert:

(i) A.C. into D.C.

(ii) D.C. into A.C.

(iii) Low voltage to high voltage and vice versa

(iv) None of these

Answer:

(iii) Low voltage to high voltage and vice versa

Question 17.

In the step up transformer:

(i) N_{S} > N_{P}

(ii) N_{S} < N_{P}

(iii) N_{S} = N_{S}

(iv) None of these

Answer:

(i) N_{S} > N_{P}

Question 18.

The value of ‘I’ given circuit is:

(i) 11A

(ii) 3A

(iii) 17A

(iv) -3A

Answer:

(iv) -3A

Question 19.

A.C. is measured by:

(i) Galvanometer

(ii) moving coil ammeter

(iii) hot wire ammeter

(iv) None of these

Answer:

(iii) hot wire ammeter

Question 20.

The ratio of r.m.s. value to peak value of A.C. is:

(i) \(\sqrt{2}\) : 1

(ii) \(\sqrt{2}\) : 1

(iii) 2 : 1

(iv) 1 : 2

Answer:

(ii) \(\sqrt{2}\) : 1

Question 21.

A.C. of 3A is the same as:

(i) 3 Coulomb/sec

(ii) 3 Ohm/meter

(iii) 3 Joule/coulomb

(iv) 3 Watt/second

Answer:

(i) 3 Coulomb/sec

Question 22.

Choke coil is used in:

(i) Reducing current in D.C. circuit

(ii) Reducing current in A.C. circuit

(iii) Changing A.C. into D.C.

(iv) Changing D.C. into A.C.

Answer:

(ii) Reducing current in A.C. circuit

Question 23.

In ac current changes

(i) only direction

(ii) magnitude only

(iii) both magnitude and direction

(iv) None

Answer:

(iii) both magnitude and direction

Question 24.

The dynamo works on the principle of:

(i) induced magnetism

(ii) coulomb’s law

(iii) electromagnetic induction

(iv) None of these

Answer:

(iii) electromagnetic induction

Question 25.

A st. conductor carrying a d.c. of i amp., is split into circualar loop as shown in fig. then the mag. induction at the centre of the loop of radius r meter is

(i) 0

(ii) ∞

(iii) \(\frac{\mu_{0} i}{2 r}\)

(iv) \(\frac{\mu_{0}}{2 \pi r}\)

Answer:

(i) 0

Question 26.

What is the relation between mobility and drift velocity

(i) \(\mu=\frac{v_{d}}{E}\)

(ii) \(\mu=\frac{E}{v_{d}}\)

(iii) µ = E,v_{d}

(iv) \(\mu=\frac{E^{2}}{v_{d}}\)

Answer:

(i) \(\mu=\frac{v_{d}}{E}\)

Question 27.

Inverse of electrical resistance is called:

(i) Electrical conductivity

(ii) Thermal conductivity

(iii) current

(iv) e.m.f.

Answer:

(i) Electrical conductivity

Question 28.

Ohm’s law does not obeyed by

(i) insulator

(ii) Semiconductor

(iii) diode

(iv) All of the above

Answer:

(iv) All of the above

Question 29.

Mean value of A.C. is given by equation:

(i) \(\frac{2}{\Pi} i_{0}\)

(ii) \(\frac{1}{\Pi} i_{0}\)

(iii) \(\frac{\Pi}{2 i_{0}}\)

(iv) \(\frac{i_{0}}{\Pi}\)

Answer:

(i) \(\frac{2}{\Pi} i_{0}\)

Question 30.

The average Power in A.C. circuit is:

Answer:

i_{rms }e_{rms} cosΦ

Question 31.

Impedence is a type of:

(i) current

(ii) e.m.f

(iii) Resistance

(iv) Power

Answer:

(iii) Resistance

Question 32.

The value of torque of a magnetic dipole is

(i) M^{2}B sinθ

(ii) \(\frac{M B}{\sin \theta}\)

(iii) \(\frac{\sin \theta}{M B}\)

(iv) MB sinθ

Answer:

(iv) MB sinθ

Question 33.

The angle of magnetic dip at the equator is:

(i) 0°

(ii) 90°

(iii) 45°

(iv) 180°

Answer:

(i) 0°

Question 34.

The angle of magnetic dip at the pole is:

(i) 0°

(ii) 90°

(iii) 45°

(iv) 180°

Answer:

(ii) 90°

Question 35.

SI unit of magnetic permeability is

(i) Henery

(ii) Weber/m

(iii) Henery/m

(iv) Tesla

Answer:

(iii) Henery/m

Question 36.

A current carrying loop is packed in x – y plane and a mag. field is switched in z-axis. The loop will

(i) move towards +ve axis

(ii) contract

(iii) move towards – x

(iv) expand

Answer:

(iv) expand

Question 37.

The cause of magnetism of a magnetic substance is:

(i) the spin motion of electrons

(ii) the pole star

(iii) the particle of the substance

(iv) the sun and the moon.

Answer:

(i) the spin motion of electrons

Question 38.

The unit of magnetic induction is:

(i) Weber amp/m^{2}

(ii) Weber

(iii) Weber/m^{2}

(iv) Weber amp/m

Answer:

(iii) Weber/m^{2}

Question 39.

Ampere’s circuital law is analogous to

(i) Gravitation law

(ii) Electrostatic coulm’slaw

(iii) Gauss’s theorem

(iv) None of these

Answer:

(iii) Gauss’s theorem

Question 40.

The ratio of magnetic intensity in end on position and in broad side on position due to small magnet is:

(i) 2 : 1

(ii) 1 : 2

(iii) \(\sqrt{2}\) : 1

(iv) 1 : \(\sqrt{2}\)

Answer:

(i) 2 : 1

Question 41.

At broad side on position of a bar magnet:

(i) magnetic field is zero

(ii) magnetic potential is zero

(iii) field and potential both are zero

(iv) None of these

Answer:

(ii) magnetic potential is zero

Question 42.

Work done in rotating a magnet of magnetic moment M in a magnetic field B is given by:

(i) MB sin θ

(ii) MB(1 – sin θ)

(iii) MB cos θ

(iv) MB (1 – cos θ)

Answer:

(iv) MB (1 – cos θ)

Question 43.

Deflection magnetometer:

(i) measures the absolute value of the magnetic moment

(ii) measures magnetic moment

(iii) compares the magnetic moment

(iv) None of these

Answer:

(iii) compares the magnetic moment

Question 44.

If be the frequency of a magnetic needle in the earth’s magnetic field (B) then:

(i) n ∝ B

(ii) n^{2} ∝ β^{2}

(iii) n^{2} ∝ β^{2}

(iv) n^{2} ∝ \(\frac{1}{B}\)

Answer:

(iii) n^{2} ∝ β^{2}

Question 45.

An electromagnet is made of:

(i) steel

(ii) soft iron

(iii) air

(iv) a mixture of copper and zinc.

Answer:

(ii) soft iron

Question 46.

SI unit of magnetic flux is

(i) ohm

(ii) Weber

(iii) Tesla

(iv) none

Answer:

(ii) Weber