Moving Charges and Magnetism Class 12 Physics MCQs Pdf
49. The magnetic field due to a straight current carrying conductor of infinite length at a perpendicular distance a is equal to _________ .
Answer/Explanation
Answer:
Explaination: \(B=\frac{\mu_{0} I}{2 \pi a}\)
50. Relation between S.I. unit and C.G.S unit magnetic field is _________ .
Answer/Explanation
Answer:
Explaination: 1 T=104 G
51. According to ampere circuital law, the line integral of the magnetic field \(\vec{B}\) around any closed path enclosing current 7, is equal to _________ .
Answer/Explanation
Answer:
Explaination: µ0I
52. Force on a charge q moving in a magnetic field B with velocity v at angle 0 is equal to _________ .
Answer/Explanation
Answer:
Explaination: F = Bqv sin θ
53. Force on a current carrying conductor in a magnetic field is _________ .
Answer/Explanation
Answer:
Explaination: F = BIl sin θ
54. The magnetic field of a straight solenoid carrying current l and having n turns per unit length is _________ .
Answer/Explanation
Answer:
Explaination: B = µ0nI
55. Why does a moving charge experience a force when placed in a magnetic field? [HOTS]
Answer/Explanation
Answer:
Explaination:
A moving charge produces a magnetic field. This magnetic field interacts with
another magnetic field of a magnet and hence, it experiences force.
56. Write the expression, in a vector form, for the Lorentz magnetic force \(\vec{F}\) due to a charge moving with velocity \(\vec{v}\) in a magnetic field \(\vec{B}\). What is the direction of the magnetic force? [Delhi 2014]
Answer/Explanation
Answer:
Explaination:
Lorentz magnetic force (\(\vec{F}_{m}\)) = q(\(\vec{v}\) × \(\vec{B}\)). The
direction of magnetic force is perpendicular to the plane containing velocity
and magnetic field vectors.
57. Define one tesla using the expression for the magnetic force acting on a particle of charge q moving with velocity \(\vec{v}\) in a magnetic field \(\vec{B}\). [Foreign 2014]
Answer/Explanation
Answer:
Explaination:
If Fmax = 1N, q = +1C and v = 1 m/s and
θ = 90°, then B = IT
Hence, one tesla is the magnetic field in which a normally entering + 1C charge,
moving at 1 ms-1 experiences a maximum force of 1 N.
58. A beam of a-particles projected along +x-axis, experiences a force due to a
magnetic field along the +y-axis. What is the direction of the magnetic field?
[AI2010]
Answer/Explanation
Answer:
Explaination:
Therefore, the direction of magnetic field is towards the negative direction of
z-axis.
59. A long straight wire carries a steady current l along the positive y-axis in a coordinate system. A particle of charge +Q is moving with a velocity \(\vec{v}\) along the x-axis. In which direction will the particle experience a force? [Foreign 2013]
Answer/Explanation
Answer:
Explaination:
By the right-hand thumb rule, the direction of magnetic field due to current /
acts normally into the plane of paper. So, \(\vec{B}=-B \hat{k}\), i.e. along
negative z-axis. The magnetic Lorentz force is given by
Thus, the force on charge +Q is along +y axis.
60. In a certain region of space, electric field \(\vec{E}\) and magnetic field \(\vec{B}\) are perpendicular to each other. An electron enters in the region perpendicular to the directions of both \(\vec{B}\) and \(\vec{E}\) and moves undeflected. Find the velocity of the electron. [Foreign 2013]
Answer/Explanation
Answer:
Explaination:
∵ qvB = qE ⇒ v = \(\frac{E}{B}\)