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Physics NEET MCQ
Magnetic Effects Of Current Mcq
Quiz 11
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Q.1
Two insulated wires of infinite length are lying mutually at right angles to each other as shown in figure. Current 2A and 1.5A respectively are flowing in them. the value of magnetic induction at point P will be
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a) 2 ×10-3 N/A-m
0%
b) 2 ×10-5 N/A-m
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c)0
0%
d)2 × 10-4 N/A-m
Explanation
Answer: (b)
Q.2
The ratio of magnetic field on the axis of current carrying coil of radius 'a' to the magnetic field at its centre will be ..
0%
a)
0%
b)
0%
c)
0%
d)
Explanation
Answer:(a)
Q.3
In a coaxial, straight cable, the central conductor and the outer conductor carry equal currents in opposite directions. The magnetic field is zero
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a) outside the cable
0%
b) inside the inner conductor
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ac) inside the outer conductor
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d) in between the two conductor
Explanation
Answer: (a)
Q.4
A hollow tube is carryings an electric current along the length distributed uniformly over its surface. The magnetic field
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a)increases linearly from the axis to the surface
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b) is constant inside the tube but non zero
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c)inside the tube is zero
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d)is zero just out side the tube
Explanation
Answer: (c)
Q.5
If a particle moves in a circular path in anti-clock wise direction after entering into a downward vertical magnetic field. The charge on the particle is
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a) positive
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b) negative
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c)neutral
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d)nothing can be said
Explanation
Answer: (a)
Q.6
In a room uniform magnetic field is acting vertically downward. When an electron moves in the horizontal plane its speed in a circular path is constant. Its path is
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a) clockwise in horizontal plane
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b) clockwise in vertical plane
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c)anti-clockwise in horizontal plane
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d)anti-clockwise in vertical plane
Explanation
Answer:(a)
Q.7
A stream of electrons is projected horizontally from right. A straight conductor carrying a current is supported parallel to electron stream and above it. If the current in the conductor is from left to right then what will be the effect on electron stream?
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a) the electron stream will be speeded up towards the right
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b) the electron stream will be retarded
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c) the electron stream will be pulled upward
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d) the electron stream will be pulled downward
Explanation
Answer: (c)
Q.8
An electron, a proton and a deuteron move in a magnetic field with same momentum perpendicularly. The ratio of radii of their circular path will be
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a)1 : 1 : 1
0%
b) 1 : 1: 2
0%
c)1 : 2 :4
0%
d)2 : 1 : 1
Explanation
Answer: (a)
Q.9
A proton, a deuteron and an α-particle moving with same momentum move in uniform perpendicular magnetic field. The ratio of the time periods of their revolution will be
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a) 2 : 1: 1
0%
b) 1/2 : 1 : 1
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c)4 : 2 : 1
0%
d)1 : 1 : 1/2
Explanation
Answer: (b)
Q.10
A proton, a deuteron and an α-particle of same kinetic energy enter in a uniform perpendicular magnetic field. The ratio of the time periods of their revolution will be
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a) 1 : √3 : 1
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b) 1 : √2 : 1
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c)1 : 2 : 2
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d)2 : 1 : 1
Explanation
Answer:(c)
Q.11
As shown in figure a wire of arbitrary shape carrying a current i between points a and b. The length of the wire is L and the distance between points a and b is d. The wire lies in a plane at right angles to uniform magnetic field B. The force on the curve wire is
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a) iLB
0%
b) idB
0%
c) i(L-d)B
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d) none of these
Explanation
Answer: (b)
Q.12
Two parallel beam of electrons moving in the same direction will
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a)repel each other
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b) attract each other
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c)not interact with each other
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d)annihilate each other
Explanation
Answer: (b)
Q.13
An inverse square law of distance is obeyed by .....
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a) the force per unit length between two long straight parallel current -carrying conductors in vacuum
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b) the electric field intensity outside an isolated charged sphere
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c)the magnetic flux density outside a long straight current-carrying wire
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d)the electrostatic potential
Explanation
Answer: (b)
Q.14
Two mutually perpendicular insulated conducting wire carrying equal currents I, intersect at origin. Then the resultant magnetic induction at point P(2m, 3m) will be ..
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a)
0%
b)
0%
c)
0%
d)zero
Explanation
Answer:(c)
Q.15
A linear conductor of length 40cm is carrying current of 3 amp is placed in magnetic field of intensity 500 gauss. If a conductor is making an angle of 30° with the field, then the force acting on it will be
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a) 3 × 104 N
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b) 3 × 102
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c) 3 ×10-2 N
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d) 3 ×10-4 N
Explanation
Answer: (c)
Q.16
Two parallel wires situated at a distance 2a are carrying equal current "i" in opposite direction as shown in figure. The value of magnetic field at apoint situated at equal distance from both the wires will be
0%
a)
0%
b)
0%
c)
0%
d)
Explanation
As shown in figure B1 and B2 are magnetic field produced by the two wires makes an angle θ with Y axis. Magnitude of both the fields is same Y component of both the fields are equal and opposite thus cancels each other while. x component will get added to to give resultant field Net magnetic field=B1sinθ + B2sinθ sinθ=a/r Answer: (d)
Q.17
A thin plastic ring of radius R having charge Q coulombs is rotated about its axis with angular frequency ω. The magnetic field intensity at the centre of the ring will be
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a)
0%
b)
0%
c)
0%
d)none of the above
Explanation
I=Qf=Q (ω/2π) and B=µoi/ 2RAnswer: (a)
Q.18
What will be magnetic field at point P in the figure below
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a)
0%
b)
0%
c)
0%
d)
Explanation
Magnetic field due to straight conductors=2 × magnetic field due to single conductor Magnetic field due to semicircular part Total magnetic field=B1 + B2 Answer:(a)
Q.19
Figure shows a long wire bent at the middle to form a right angle. the magnitude of the magnetic fields at the points P, Q, R, S are equal its value will be ..
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a) µoi/4πd
0%
b) µoi/2πd
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c) µoi/πd
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d) µoi/d
Explanation
Answer: (a)
Q.20
When a proton is released from rest in a room, it starts with an initial acceleration a0 towards west. When it is projected towards north with a speed v0 it moves with an initial acceleration 3a0 toward west. The electric and magnetic fields in the room are
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a)
0%
b)
0%
c)
0%
d)
Explanation
First case :Protons released from rest thus no magnetic force act on it, Proton moves along with direction of electric field. Thus electric field direction is along west direction Now F= eE and Fma0 eE=ma0 Second case: Proton moves with initial velocity projected towards north moves along west. Thus proton experience electric filed and magnetic field Now j × n must be -i It will be possible is n = -k or direction of magnetic field is down ward direction Now above equation reduced to Answer:(b)
Q.21
A current loop in a magnetic field … [ NEET 2013]
0%
a) Experiences a torque whether the field isuniform or non-uniform in all orientations
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b) Can be in equilibrium in one orientation
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c) Can be in equilibrium in two orientations, boththe equilibrium states are unstable
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d) Can be in equilibrium in two orientations, onestable while the other is unstable
Explanation
Parallel M– stable Anti-parallel M– unstable Answer:(d)
Q.22
Two identical long conducting wires AOB and COD are placed at right angle to each other,with one above other such that 'O' is theircommon point for the two. Thewires carry I1and I2 currents respectively. Point 'P' is lying at distance’d’ from 'O' along a directionperpendicular to theplane containing the wires.Themagnetic field at the point 'P'will be
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a)
0%
b)
0%
c)
0%
d)
Explanation
Point P is exactly above O at distance d, angle between the magnetic field produced is 90° Answer:(d)
Q.23
A wire carrying current I has the shape as shown in adjoining figure. Linear parts of the wire are verylong and parallel to X-axis while semicircular portion of radius R is lying in Y-Z plane. Magneticfield at point O is : … [ AIPMT 2015]
0%
a)
0%
b)
0%
c)
0%
d)
Explanation
Very log conductor produces magnetic field at point is at one end of conductor at distance r, which is centre of the semicircular position Direction of magnetic field due to both wire is in same directionof axis -Z Thus Magnetic field at centre of semicircular centre position is given by for semicircle θ = π and direction negative X axis B1 and B2 are perpendicular to each other B = (B1 ) +(B1 ) Answer:(d)
Q.24
An electron moving in a circular orbit of radius r makes n rotations per second. The magnetic fieldproduced at the centre has magnitude :
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a)
0%
b)
0%
c) zero
0%
d)
Explanation
Electron is orbiting around nucleus, can be consider as current in circular coil B=(μ0 I)/2r Now current I =Q/t Given electron moves n times in one second thus Q = ne , t=1sec, I = ne B=(μ0 ne)/2r Answer:(a)
Q.25
A proton and an alpha particle both enter a regionof uniform magnetic field, B, moving at right anglesto the field B. If the radius of circular orbits for boththe particles is equal and the kinetic energy acquiredby proton is 1 MeV, the energy acquired by thealpha particle will be :-
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a) 1 MeV
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b) 4 MeV
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c) 0.5 MeV
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d) 1.5 MeV
Explanation
Similarly As qA=2qP and mA =4 mP As EP = 1MeV EA =1 MeV Answer:(a)
Q.26
A square loop ABCD carrying a current i, is placed near and coplanar with a long straight conductorXY carrying a current I, the net force on the loopwill be :-
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a)
0%
b)
0%
c)
0%
d)
Explanation
Magnetic force on BC and AD is equal and opposite and cancels each other effect. Magnetic field produced by Current is given by Force on conductor carrying current is given by BiL Force on side AB Force on CD Direction of F1 is towards conductor XY and F2 is opposite due to opposite direction of current. Thus net force Answer:(a)
Q.27
The magnetic susceptibility is negative for :
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a) diamagnetic material only
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b) paramagnetic material only
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c) ferromagnetic material only
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d) paramagnetic and ferromagnetic materials
Explanation
Answer:(a)
Q.28
A long straight wire of radius a carries a steadycurrent I. The current is uniformly distributed overits cross-section. The ratio of the magnetic fieldsB and B', at radial distancesa/2and 2a respectively,from the axis of the wire is : … [AIPMT 2015]
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a) 1/4
0%
b) 1/2
0%
c) 1
0%
d) 4
Explanation
For the point inside the wire For point outside the wire According to the equation Answer:(c)
Q.29
A long solenoid has 1000 turns. When a current of 4A flows through it, the magnetic flux linked with each turn of the solenoid is 4×10-3Wb. The self inductance of the solenoid is
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a) 4H
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b) 3H
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c) 2H
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d) 1H
Explanation
Flux linked with each turn = 4×10-3Wb ∴ Total flux linked Φ = 1000(4×10-3) Wb = 4Wb Φ = LI 4= L (4) ⇒ L = 1 H Answer:(d)
Q.30
A long wire carrying a steady current is bent intoa circular loop of one turn. The magnetic field atthe centre of the loop is B. It is then bent into acircular coil of n turns. The magnetic field at thecentre of this coil of n turns will be … [NEET II 2016]
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a) 2nB
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b) 2n2B
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c) nB
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d) n2B
Explanation
L=2πR If one turn If n turns then L=n2πr Answer:(d)
0 h : 0 m : 1 s
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