# Magnetic Effects of Current Mock Test-1

Questions No:1

A charged particle P leaves the origin with speed v = v0, at some inclination with the x-axis. There is a uniform magnetic field B along the x-axis. P strikes a fixed target Ton the x-axis for a minimum value of B = B0. P will also strike T if

[A] B = 2B0, v=2v0
[B] B = 2B0, v = v0
[C] Both are correct
[D] Both are wrong

Questions No:2

An ionized gas contains both positive and negative ions initially at rest. If it is subjected simultaneously to an electric field along the +x direction and a magnetic field along the +z direction then

[A] positive ions deflect towards +y direction and negative ions -y direction
[B] all ions deflect towards +y direction
[C] all ions deflect towards -y direction
[D] positive ions deflect towards -y direction and negative ions towards +y direction

Questions No: 3

Two protons are projected simultaneously from a fixed point with the same velocity v into a region where there exists a uniform magnetic field. The magnetic field strength at Band it is perpendicular to the initial direction of v. One proton starts at time t = 0 and another proton at t = $$\frac{πm}{2qB}$$ . The separation between them at time t = $$\frac{πm}{qB}$$where m and q are the mass and charge of proton, will be approximately

[A]2 $$\frac{mv}{qB}$$

[B]$$\frac{\sqrt2πm}{2qB}$$

[C]$$\frac{mv}{qB}$$

[D]$$\frac{mv}{2qB}$$

Questions No: 4

A disc of radius R rotates with constant angular velocity ω about its own axis. Surface charge density of this disc varies as σ = αr2 where r is the distance from the centre of disc. Determine the magnetic field intensity at the centre of disc

[A]μ0α ωR3
[B]μ0α ωR3/6
[C]μ0α ωR3/8
[D]μ0α ωR3/3

Questions No:5

A particle of mass m and having a positive charge q is projected from origin with speed v0 along the positive x-axis in a magnetic field B = – B0k where B0 is a positive constant. If the particle passes through (0, y, 0), then y is equal to
[A]-$$\frac {2mv_0}{qB_0}$$

[B]$$\frac {mv_0}{qB}$$

[C]-$$\frac {mv_0}{qB}$$

[D]$$\frac {2mv_0}{qB_0}$$

Questions No:6

A rigid circular loop of radius” r” and mass “m” lies in the xy plane on a flat table and has a current “I” flowing in it. At this particular place the earth’s magnetic field is B = Bxi + Bz i. The value of “I” so that the loop starts tilting is

[A]-$$\frac {mg}{πr\sqrt{B_x^2+B_z^2}}$$

[B]-$$\frac{mg} {πrB_0 }$$

[C]-$$\frac{mg} {πrB_z }$$

[D]-$$\frac {mg}{πr\sqrt{B_xB_z}}$$

Questions No:7

Two circular coils 1 and 2 are made from the same wire but the radius of the 1st coil is twice that of the 2nd coil. What is the ratio of potential difference applied across them, so that the magnetic field at their centres is the same?

[A] 3
[B] 4
[C] 6
[D] 2

Questions No: 8

A charged particle with specific charge (charge per unit mass =(q/m) = s) moves undeflected through a region of space containing mutually perpendicular and uniform electric and magnetic fields E and B. When the E field is switched off, the particle will move in a particular path of radius

[A]$$\frac {E}{Bs}$$

[B]$$\frac {Es}{B}$$

[C]$$\frac {Es}{B^2}$$

[D]$$\frac {E}{B^2s}$$

Questions No:9

A circular flexible loop of wire of radius r carrying a current I is placed in a uniform magnetic field B perpendicular to the plane of the circle so that wire comes under tension. If B is doubled, tension in the loop

[A] remains unchanged
[B] is doubled
[C] is halved
[D] becomes 4 times

Questions No:10

A conducting rod of length L and mass m is moving down a smooth inclined plane of inclination 9 with constant speed v. A current I is flowing in the conductor perpendicular to the paper inwards. A vertically upward magnetic field B exists in space there. The magnitude of magnetic field B is
[A]$$\frac{B}{v}$$

[B]$$\frac{v}{B}$$

[C]$$\sqrt{\frac{B}{v})}$$

[D]$$\sqrt{\frac{v}{B})}$$

Questions No:11

The magnetic field existing in a region is given by
B=B0[1+$$\frac{x}{l}$$]
A square loop of edge “e” and carrying current “I” is placed with its edges parallel to the x-y axis. The magnitude of the net magnetic force experienced by the loop is

[A] 2B0Ie
[B] zero
[C] B0Ie
[D] 4B0Ie

Questions No:12

A charge q is moving with a velocity v1 =1i m/s at a point in a magnetic field and experiences a force F = g[-j + 1k] N. If the charge is moving with a velocity v2 = 2 j m/s at the same point, it experiences a force F2 = q(1i – 1k) N. The magnetic induction B at that point is

[A] (i + j + k) Wb/m2
[B] (i – j + k) Wb/m2
[C] (-i + j – k) Wb/m2
[D] (i + j- k) Wb/m2 Wb/m2

Questions No:13

A particle of specific charge (q/m) = π C/kg is projected from the origin towards positive x-axis with a velocity of 10 m/s in a uniform magnetic field B =-2kT. The velocity v of the particular after time t = $$\frac{1}{6}$$ will be

[A] (5i + $$5\sqrt{3} j$$) m/s

[B]10j m/s

[C] ($$5\sqrt{3} i$$ + 5j) m/s

[D] -10 j m/s

Questions No:14

A proton moving with a constant velocity passes through a region of space without any change in its velocity. If E and B represent the electric and magnetic fields respectively, then this region of space may have

[A] E=0, B=0
[B] E=0, B≠0
[C] E≠0, B = 0
[D]E≠=0,B≠=0

Questions No:15

Two particles X and Y having equal charges, after being accelerated through the same potential difference, enter a region of uniform magnetic field and describe circular path of radius R1 and R2 respectively. The ratio of mass of X to that of Y is

[A]$$\sqrt\frac{R_1}{R_2}$$

[B]$$\frac{R_2}{R_1}$$

[C]$$(\frac{R_1}{R_2})^2$$

[D]$$\frac{R_1}{R_2}$$

Questions No:16

H+,He+ and O2+ ions having same kinetic energy pass through a region of space filled with uniform magnetic field B directed perpendicular to the velocity of ions. The masses of the ions H+,He+ and O2+ are respectively in the ratic 1 : 4 : 1 6. As a result

[A] H+ ions will be deflected most
[B] O2+ ions will be deflected least
[C] He+ and O2+ ions will suffer same deflection
[D] All ions will suffer same deflection

Questions No:17

Assertion : In a uniform magnetic field B = B0 k, if velocity of a charged particle is v0i at t =0, then it can have the velocity v0j at some other instant.

Reason:In uniform magnetic field acceleration of a charged particle is always zero.

[A] If both Assertion and Reason are true and Reason is the correct explanation of Assertion.
[B] If both Assertion and Reason are true but Reason is not correct explanation of Assertion.
[C] If Assertion is true but Reason is false.
[D] If Assertion is false but Reason is true.
[E]If both Assertion and Reason are false

Questions No:18

Assertion: A charged particle moves perpendicular to a uniform magnetic field then its momentum remains constant.

Reason: Magnetic force acts perpendicular to the velocity of the particle.

[A] If both Assertion and Reason are true and Reason is the correct explanation of Assertion.
[B] If both Assertion and Reason are true but Reason is not correct explanation of Assertion.
[C] If Assertion is true but Reason is false.
[D] If Assertion is false but Reason is true.
[E]If both Assertion and Reason are false

Questions No:19

Assertion: A beam of electron can pass undeflected through a region of E and B.

Reason: Force on moving charged particle due to magnetic field may be zero in some cases.

[A] If both Assertion and Reason are true and Reason is the correct explanation of Assertion.
[B] If both Assertion and Reason are true but Reason is not correct explanation of Assertion.
[C] If Assertion is true but Reason is false.
[D] If Assertion is false but Reason is true.
[E]If both Assertion and Reason are false

Questions No:20

Assertion: If the path of a charged particle in a region of uniform electric and magnetic field is not a circle, then its kinetic energy may remain constant.

Reason: In a combined electric and magnetic field region, a moving charge experiences a net force F =qE +q(v x B) where symbols have their usual meanings.

[A] If both Assertion and Reason are true and Reason is the correct explanation of Assertion.
[B] If both Assertion and Reason are true but Reason is not correct explanation of Assertion.
[C] If Assertion is true but Reason is false.
[D] If Assertion is false but Reason is true.
[E]If both Assertion and Reason are false