SikhLo - Current Affairs in Hindi, Daily current affairs, Current affairs

 Bihar Board 12th Physics Objective Important Questions Part 2

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) 1r
(iii) 1r2
(iv) r2
Answer:
(ii) 1r

Question 2.
In for V ~ I graph for a conductor at temp. T1 & T2 is shown (T2 – T1) 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 reln. among the electric field (E⃗ ), current density J⃗  and resistivity (ρ) is:
(i) E⃗ =ρJ⃗ 
(ii) J⃗ =ρE⃗ 
(iii) ρ=ρE⃗ ⋅J⃗ 
(iv) None of these
Answer:
(i) E⃗ =ρJ⃗ 

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 2i^ +3j^ and it is subjected to magnetic field of 4k^, 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) NS > NP
(ii) NS < NP
(iii) NS = NS
(iv) None of these
Answer:
(i) NS > NP

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) 2–√ : 1
(ii) 2–√ : 1
(iii) 2 : 1
(iv) 1 : 2
Answer:
(ii) 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) μ0i2r
(iv) μ02πr
Answer:
(i) 0

Question 26.
What is the relation between mobility and drift velocity
(i) μ=vdE
(ii) μ=Evd
(iii) µ = E,vd
(iv) μ=E2vd
Answer:
(i) μ=vdE

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) 2Πi0
(ii) 1Πi0
(iii) Π2i0
(iv) i0Π
Answer:
(i) 2Πi0

Question 30.
The average Power in A.C. circuit is:

Answer:
irms erms 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) M2B sinθ
(ii) sinθ
(iii) sinθ
(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/m2
(ii) Weber
(iii) Weber/m2
(iv) Weber amp/m
Answer:
(iii) Weber/m2

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) 2–√ : 1
(iv) 1 : 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) n2 ∝ β2
(iii) n2 ∝ β2
(iv) n2 ∝ 1B
Answer:
(iii) n2 ∝ β2

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