21. If the flow of electric current is parallel to the magnetic field, the force will be?
A. Zero
B. Infinity
C. Maximum
D. Half the original value
Answer: A
Force is a cross-product. A cross product involves the sine of the angle between them. If two quantities are parallel to each other, the angle between them is zero. Sin(0) is zero, hence force is zero.
22. The ratio of magnetic force to electric force on a charged particle getting undeflected in a field is ______
A. 1
B. 0
C. 2
D. 4
Answer: A
When a charged particle is undeflected in a field, the magnitude of the magnetic force and electric force acting on the particle is the same, hence the ratio is 1.
23. Weakest force in nature is __________
A. Electric force
B. Gravitational force
C. Weak force
D. Magnetic force
Answer: A
Gravitational force is the weakest force in nature as it does not bind anything strongly with its help.
24. 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 are mutually perpendicular to each other.
25. 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 are mutually perpendicular to each other.
25. 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.
26. 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.
27. When the length of the conductor 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 length of the conductor increases because it is directly proportional to the force.
28. When the magnetic field intensity 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 magnetic field intensity increases because it is directly proportional to the force.
29. 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.
30. 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.
