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12th Grade > Physics

MAGNETIC EFFECTS OF CURRENT MCQs

Magnetic Effects Of Electric Current, Magnetic Effects Of Current(10th And 12th Grade)

Total Questions : 54 | Page 2 of 6 pages
Question 11. Which of the following materials is the most suitable for making the core of an electromagnet?
  1.    Soft iron
  2.    Brass
  3.    Aluminium
  4.    Steel
 Discuss Question
Answer: Option A. -> Soft iron
:
A
Soft iron can be used as the core of an electromagnet because it loses all of its magnetism when the current in the coil is switched off. On the other hand, steel retains its magnetism even after the current is switched off.
Brass and aluminium are non-magnetic materials. Hence, they can not be used as the core of an electromagnet.
Question 12. According to the right-hand thumb rule, if the thumb points in the direction of current,  then the other fingers encircle in the direction of the _____.
  1.    motion
  2.    force
  3.    magnetic field
  4.    current
 Discuss Question
Answer: Option C. -> magnetic field
:
C
According to the right-hand thumb rule, if you are holding a current carrying conductor with the right hand in such a way, that the thumb points in the direction of the current then the direction in which the other fingers encircle the conductor gives the direction of the magnetic field.
According To The Right-hand Thumb Rule, If The Thumb Points ...
Question 13. A current I flows along the length of an infinitely long, straight and thin-walled pipe. Choose the correct option?
  1.    The magnetic field at all points inside the pipe is the same but not zero
  2.    The magnetic field at any point inside the pipe is zero
  3.    The magnetic field is zero only on the axis of the pipe
  4.    The magnetic field is different at different points inside the pipe
 Discuss Question
Answer: Option B. -> The magnetic field at any point inside the pipe is zero
:
B
Applying Ampere's law B.dl=μ0i to any closed path inside the pipe, we can understand that as the currect enclosed inside it is zero, the magnetic field will be equal to zero.
Question 14. Two long wires are hanging freely. They are joined first in parallel and then in series and then are connected with a battery. In both cases, which type of force acts between the two wires
  1.    Attraction force when in parallel and repulsion force when in series
  2.    Repulsion force when in parallel and attraction force when in series
  3.    Repulsion force in both cases
  4.    Attraction force in both cases
 Discuss Question
Answer: Option A. -> Attraction force when in parallel and repulsion force when in series
:
A
When connected in parallel the current will be in the same direction hence the wires attract each other and when connected in series the current will be in the opposite direction. Hence they repel each other.
Two Long Wires Are Hanging Freely. They Are Joined First In ...

Question 15. Two very long, straight and parallel wires carry steady currents I and I respectively. The distance between the wires is d. At a certain instant of time, a point charge q is at a point equidistant from the two wires in the plane of the wires. Its instantaneous velocity v is perpendicular to this plane. The magnitude of the force due to the magnetic field acting on the charge at this instant is                                         
  1.    μ0Iqv2πd                            
  2.    μ0Iqvπd  
  3.    2μ0Iqvπd  
  4.    0
 Discuss Question
Answer: Option D. -> 0
:
D
According to gives information following figure can be drawn, which shows that direction of magnetic field is along the direction of motion of charge so net force on it is zero.
if the currents are parallel then the net magnetic field at midpoint will be zero, Hence, no magnetic force acts on it.
Two Very Long, Straight And Parallel Wires Carry Steady Curr...
Question 16. A current I flows in circular arc of wire which subtends an angle θ at the centre. If the radius of the circle is r  then the magnetic field B at center is:
  1.    μ0ir
  2.    μ0i2r
  3.    3μ0i4r
  4.    (θ∘360∘)μ0i2r
 Discuss Question
Answer: Option D. -> (θ∘360∘)μ0i2r
:
D
B=μ0i4πr[θ]
B=(θ360)μ0i2r
Question 17. An electron is revolving around a proton in a circular orbit of radius 12A. If it produces a magnetic field of 14 T, its angular velocity in rad/s
  1.    4×1016  
  2.    4×10−15
  3.    4×1017
  4.    4×1018
 Discuss Question
Answer: Option A. -> 4×1016  
:
A
B=μ0wq4πr;14=4π×107w×1.6×10194π×12×1010=71.6×1016=4×1016rads1
Question 18. The magnetic field at the centre of the circular coil carrying current of 4A is
The Magnetic Field At The Centre Of The Circular Coil Carryi...
  1.    8π3×10−5T
  2.    8π3×10−4T
  3.    2π×10−5T
  4.    2π×10−4T
 Discuss Question
Answer: Option C. -> 2π×10−5T
:
C
B=μ0i2r[θ2π]=4π107×42×3×102[3π22π]=2π×105T
Question 19. Two wires are wound into coils of one turn and three turns of equal radius. If the same current is passed through the coils, the ratio of magnetic field at their centres will be:
  1.    1:4
  2.    1:9
  3.    9:1
  4.    1:3
 Discuss Question
Answer: Option B. -> 1:9
:
B
Bαn2B1B2=[n1n2]2=[13]2B1:B2=1:9
Question 20. A closed circuit is in the form of a regular hexagon of side a. If the circuit carries current I, What is magnetic induction at the cetre of the hexagon?
  1.    √3μ0iπa
  2.    √3μ0iπa
  3.    zero 
  4.    None
 Discuss Question
Answer: Option A. -> √3μ0iπa
:
A
α=βB=6[μi4πr(sinα+sinβ)]=6[μoi4πr2sin30]=6μ0i×2×122π3ahere,r=a2a24=3a2
=3μ0iπa
A Closed Circuit Is In The Form Of A Regular Hexagon Of Side...

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