JEE Advanced (Single Correct Type): Moving Charges & Magnetism | Chapter-wise Tests for JEE Main & Advanced PDF Download

Q.1. In the given figure, what is the magnetic field induction at point O?
(a)
(b)
(c)
(d)

Correct Answer is option (c)


B₁ = 0 ⇒ B₀ = B₂ + B₃
⇒
⇒

Q.2. Electrons at rest are accelerated by a potential of V volt. These electrons enter the region of space having a uniform, perpendicular magnetic induction field B. The radius of the path of the electrons inside the magnetic field is
(a)
(b)
(c)
(d) 

Correct Answer is option (b)
The gain in K.E. of the electron after moving through the potential difference
⇒
⇒

Q.3. An infinitely long straight conductor is bent into shape as shown in figure. It carries a current I A. and the radius of circular loop is r metre. Then the magnetic induction at the centre of the circular loop is:
(a) 0
(b) ∞
(c)
(d) 

Correct Answer is option (d)

B₀ =B₁ – B₂ + B₃
⇒
⇒

Q.4. In a hydrogen atom the electron is making 6.6 x 10¹⁵ revolutions per second in a circular orbit of radius 0.53 A^o . The field of induction produced at the position of the nucleus is approximately (T - Tesla).
(a)  zero
(b) 3πT
(c) 4π T
(d) 0.4πT

Correct Answer is option (c)

ω = 2π  x  6.6 x 10¹⁵

= 3.98 ≈ 4πT

Q.5. Alpha particles (m = 6.7 x 10^-27 kg, q = +2e) are accelerated from rest through a potential difference of 6.7 kV. Then, they enter a magnetic field B = 0.2 T perpendicular to them direction of their motion. The radius of the path described by them is
(a)  8.375 m
(b)  8.375 cm
(c)  infinity
(d)  none of these 

Correct Answer is option (b)

⇒
=
=
= 0.08375 m
= 8.375 cm

Q.6. A long straight wire along the z-axis carries a current I in the negative z direction. The magnetic vector field  at a point having coordinates (x, y) in the z = 0 plane is
(a)
(b)
(c)
(d)

Correct Answer is option (a)

Q.7. A circular coil of radius r carries a current I.  If the same coil is now changed into a square loop carrying the same current, magnitude of its magnetic moment will
(a) increase
(b) decrease
(c) remain constant
(d) change depending upon the value of r 

Correct Answer is option (b)
A₁ = πr²
A₂ = L2
2πr = 4L

∴ A₂ > A₁
Hence, magnetic moment will increase.

Q.8. Through two parallel wires A and B, 10 A and 2 A currents are passed, respectively, in opposite directions. If the wire A is infinitely long and the length of wire B is 2 m, then what will be the force on the conductor B which is situated 10 cm away from A?
(a) 6 x 10^-5  N
(b) 9 x 10^-5 N
(c) 8 x 10^-5 N
(d) 10 x 10^-5 N 

Correct Answer is option (c)

= 8 x 10^-5 N

Q.9. An alpha particle and proton have same velocity when enter uniform magnetic field. The period of rotation of proton will be
(a) double of that of a particle
(b) four times that of a particle
(c) one half times that of a particle
(d) same as that of a particle.

Correct Answer is option (c)

⇒

Q.10. A magnitude field of   tesla exerts a force of  x 10^{– 10}N on a particle having charge of 1 x 10^–9C and moving in x – y plane. The velocity of particle is
(a)
(b)
(c)
(d) 

Correct Answer is option (c)


3 x 10^-10 = -x x  0.004 x 10^-9

y = 100

Q.11. A proton, a deuteron and ana particle having same kinetic energy are moving in circular trajectories in a constant magnetic field. If r_P ,r_d and r_α denote respectively the radii of trajectories of these particles, then,
(a) r_α = r_P < r_d
(b) r_α > r_P > r_d
(c) r_α = r_d > r_p
(d) r_P = r_d = r_α

Correct Answer is option (a)


⇒ r_P = r_α < r_d

Q.12. A circular loop of mass m and radius r is kept in a horizontal position (X-Y plane) on a table as shown in figure. A uniform magnetic field B is applied parallel to xaxis. The current I in the loop, so that its one point just lifts from the table, is:
(a) mg/πr²B
(b) mg/πrB
(c) mg/2πrB
(d) πrB/mg 

Correct Answer is option (b)
The magnetic moment of the loop is m = πr² I.


⇒ g = πr² IB.
For the loop to be just lifted,
mg r = πr² IB
⇒

Q.13. The magnetic field strength at a point P distant r due to an infinite straight wire as shown in the figure carrying a current i is:
(a) μ₀
(b)
(c)
(d)

Correct Answer is option (d)
Magnetic field at P due to each of the straight wire will be directed inward and has the magnitude (sin 45° + sin 90°). Thus net field at P is

Q.14. A wire bent in the form of a sector of radius r subtending an angle θ^o at centre, as shown in figure is carrying a current i. The magnetic field at O is:
(a)
(b)
(c)
(d) zero

Correct Answer is option (c)
The magnetic field  B = θ/360^oB₀;
where B0 = magnetic field due to a circular loop =
⇒

Q.15. The conductor abcd carries a current of 4 A. The field at the centre O of the circular part of it is  

(a)

(b) 2π x 10^–5 T
(c)  
(d) 2π x 10^-4T

Correct Answer is option (b)

=
= 2π x 10^–5 T

Q.16. A copper wire having resistance 0.01 ohm in each metre is used to wind a 400 turn solenoid of radius 1 cm and length 20 cm. Find the e.m.f of the battery which when connected across the solenoid will produce a magnetic field 1 x 10^–2 tesla at the centre of solenoid.
(a) 1 volt
(b) 2 volts
(c) 2.5 volts
(d) 3 volts 

Correct Answer is option (a)
One turn has a length = 2πr = 2π x 1  x 10^–2m
No. of turns  = 400
∴ Total length  = 400  x  2π x 10^–2 m
Resistance (R) = 400 x 2π x 10^–2 x 0.01 ohm
= 800 π x 10^–4 ohm
Magnetic field = μ₀ni
1 x 10^–2 =
But i =


= 1 volt

Q.17. Currents of 3 A, 1 A and 2 A flow through the long, straight and parallel conductors a, b and c respectively as shown. A length 0.5 m of wire b experiences a force of

(a) 10.0 x 10^–6 N from right to left
(b) 10.0 x 10^–6 N from left to right
(c) 5.0 x 10^–6 N from right to left
(d) 5.0 x10^–6 N from left to right

Correct Answer is option (d)
Force between the conductors a and b =  towards right.
Force between the conductors c and b =  N/m towards left.
 N/m towards right

Q.8. Alpha particles (m = 6.7 x 10^–27 kg, q = + 2e) are accelerated from rest through a potential difference of 6.7 kV. Then they enter a magnetic field B = 0.2 T perpendicular to their direction of motion. The radius of the path described by them is
(a) 8.375 m
(b) 8.375 cm
(c) infinity
(d) none of the above

Correct Answer is option (b)

= 8.375  x 10^–2 m  

Q.19. A particle of charge +q and mass m moving under the influence of a uniform electric field  and a uniform magnetic field   follows a trajectory from P to Q as shown in Figure.  The velocity at P and Q are v and -  . Which of the following statement/s is/are correct?

(a)
(b) Rate of work done by the electric field at P is
(c)  Rate of work done by the electric field at P is zero
(d) Rate of work done by both of the fields at Q is different. 

Correct Answer is option (b)
Work done by electric filed = Gain in kinetic energy
⇒
⇒
Rate of work done by electric filed at P =  
=
=

Q.20. A disc of mass m has a charge Q distributed on its surface. It is rotating about an XX' with a angular velocity ω. The force acting on the disc is, the magnetic field is B.

(a) zero
(b) ωRB/π
(c) 2QωBR
(d) none of these

Correct Answer is option (a)
Since all the currents form closed loops in the uniform magnetic field, the force acting on the disc is zero.