51. The relation between the direction of force and the direction of the magnetic field is __________
A. Same direction
B. Opposite direction
C. Perpendicular
D. Unrelated
Answer: C
When a conductor carries a certain value of current, the force developed in the conductor, the current in the conductor, and the magnetic field in the conductor is mutually perpendicular to each other.
52. The relation between the direction of current and the direction of the force is ________
A. Same direction
B. Opposite direction
C. Perpendicular
D. Unrelated
Answer: C
When a conductor carries a certain value of current, the force developed in the conductor, the current in the conductor, and the magnetic field in the conductor is mutually perpendicular to each other.
51. Which among the following, is the correct expression for force in a current-carrying conductor if the magnetic field is perpendicular to it?
A. F = Bi
B. F = B2il
C. F = Bil
D. F = Bl2
Answer: C
The correct expression for force in a current-carrying conductor in a magnetic field perpendicular to it is F = Bil, where B is the magnetic field, i is the current in the conductor and l is the length of the conductor.
52. When the current in the current-carrying conductor increases, what happens to the force in the conductor which is at right angles to the magnetic field?
A. Increases
B. Decreases
C. Remains the same
D. Becomes zero
Answer: A
The force at right angles to the magnetic field of a current-carrying conductor increases when the current increases because it is directly proportional to the force.
55. The unit for force in a current-carrying conductor is _________
A. Tesla × Ampere × meter
B. Tesla
C. Ampere/meter
D. Ampere × meter
Answer: A
The Magnetic Force on a Current is expressed as
F = B × i × l.
So, a unit of force = unit of B × unit of I × unit of l = Tesla × Ampere × meter.
56. If the net force is zero on a particle in a magnetic field what is the relation between velocity and magnetic field?
A. v = E × B
B. v = E/B
C. v = B/E
D. v = 1/(E × B)
Answer: B
Since net force is zero on the particle.
Electric force = Magnetic force
QE = QvB = > E = vB or v = E/B.
57. If the intensity of the magnetic field is 100T, the length of the conductor is 10m and the magnitude of force perpendicular to the magnetic field is 10kN, calculate the current in the conductor.
A. 100 A
B. 100 mA
C. 10 A
D. 10 mA
Answer: C
The formula for calculating the value of the force which is perpendicular to the magnetic field is:
F = Bil
Substituting the values from the question, we get i = 10A.
58. If the intensity of the magnetic field perpendicular to the current-carrying conductor is 100T, the length of the conductor is 3m and the current in the conductor is 10A, calculate the magnitude of force perpendicular to the electric field.
A. 300N
B. 30N
C. 30kN
D. 3kN
Answer: D
The formula for calculating the value of the force which is perpendicular to the magnetic field is:
F = Bil
Substituting the values from the question,
we get F = 3kN.
59. Force in a current-carrying conductor placed in a magnetic field is ___________ of il and B.
A. dot product
B. scalar product
C. cross product
D. vector addition
Answer: C
Force in a current-carrying conductor is given by the cross product of il and B.
F = BIL
Where
F is a force in newtons (N)
B is magnetic flux density (magnetic field strength) in tesla (T)
I is current in amperes – also referred to as amps (A)
60. An E.M.F. can be induced by _________
A. Change in the magnetic field only
B. Change in the area of cross-section only
C. Change in angle between magnetic field and area only
D. Change in the magnetic field, area, or angle between them
Answer: D
The EMF induced is
emf = -dϕ/dt.
We know ϕ flux is the dot product of the magnetic field vector and area vector.
ϕ = BAcos(θ),
hence if either of the three, that is, magnetic field, area, or angle changes, the emf will change, and flux changes due to which emf can be induced.
