Magnetic Effects of Current and Magnetism – JEE Physics Questions with Solutions

Q1. AI-generated practice Single-correct MCQ Easy

A proton moves with a speed of 2 × 10⁶ m/s perpendicular to a uniform magnetic field of 0.5 T. The magnitude of the force on it is (e = 1.6 × 10^-19 C):

A6.4 × 10^-14 N
B3.2 × 10^-13 N
C1.6 × 10^-13 N
D1.6 × 10^-19 N

Q2. AI-generated practice Single-correct MCQ Easy

The work done by a uniform magnetic field on a charged particle moving through it is:

A
zero
B
positive if the particle is positive
C
equal to its kinetic energy
D
qvB

Q3. AI-generated practice Single-correct MCQ Medium

An electron moving at 1 × 10⁶ m/s enters a uniform magnetic field of 1 × 10^-3 T perpendicular to its velocity. The radius of its circular path is about (m_e = 9.1 × 10^-31 kg, e = 1.6 × 10^-19 C):

A
57 mm
B
10.4 m
C
0.57 mm
D
5.7 mm

Q4. AI-generated practice Single-correct MCQ Medium

A charged particle moves in a circle in a uniform magnetic field. If its speed is doubled, its time period of revolution:

A
is halved
B
remains the same
C
becomes four times
D
doubles

Q5. AI-generated practice Single-correct MCQ Medium

A charged particle enters a uniform magnetic field with its velocity making an angle of 30° with the field. Its path in the field is:

A
a parabola
B
a helix with axis along the field
C
a circle
D
a straight line

Q6. AI-generated practice Single-correct MCQ Hard

A proton moving at 4 × 10⁵ m/s enters a uniform magnetic field of 0.1 T with its velocity at 60° to the field. The pitch of its helical path is about (m_p = 1.67 × 10^-27 kg, e = 1.6 × 10^-19 C):

A
6.6 cm
B
3.6 cm
C
23 cm
D
13 cm

Q7. AI-generated practice Single-correct MCQ Medium

In a region with crossed electric and magnetic fields, E = 3 × 10⁴ V/m and B = 0.2 T, mutually perpendicular. Charged particles pass through undeflected (moving perpendicular to both fields) if their speed is:

A1.5 × 10⁵ m/s
B1.5 × 10⁴ m/s
C6 × 10³ m/s
D6.7 × 10^-6 m/s

Q8. AI-generated practice Single-correct MCQ Medium

A proton and an α-particle have the same kinetic energy and move perpendicular to the same uniform magnetic field. The ratio of their radii r_p : r_α is (m_α = 4m_p, q_α = 2e):

A
2 : 1
B
1 : √2
C
1 : 2
D
1 : 1

Q9. AI-generated practice Single-correct MCQ Hard

An electron and a proton move with the same speed perpendicular to the same uniform magnetic field. The ratio of the radius of the proton's path to that of the electron's path is:

A
about 1836
B
1
C
about 1/1836
D
about 43

Q10. AI-generated practice Single-correct MCQ Easy

A positively charged particle moves along the +x axis in a uniform magnetic field directed along +y. The magnetic force on it is directed along:

A
−z
B
−x
C
+z
D
+y

Q11. AI-generated practice Single-correct MCQ Medium

An electron moves along the +x axis in a uniform magnetic field directed along +z. The magnetic force on the electron is directed along:

A
+z
B
+y
C
−x
D
−y

Q12. AI-generated practice Single-correct MCQ Hard

A particle of mass m and charge q, initially at rest, is accelerated through a potential difference V and then enters a uniform magnetic field B perpendicular to its velocity. The radius of its circular path is:

A
(1/B)√(mV/2q)
B
(mV)/(qB)
C
(1/B)√(2mV/q)
D
√(2qV/m)/B

Q13. AI-generated practice Single-correct MCQ Medium

The frequency of revolution of a proton moving in a uniform magnetic field of 1 T is about (m_p = 1.67 × 10^-27 kg, e = 1.6 × 10^-19 C):

A
1.5 MHz
B
15 MHz
C
96 MHz
D
150 MHz

Q14. AI-generated practice Single-correct MCQ Hard

A charged particle is released from rest in a region where a uniform electric field and a uniform magnetic field are parallel to each other. The particle moves:

A
in a straight line along the fields with increasing speed
B
in a circle
C
in a helix of constant pitch
D
along a cycloid

Q15. AI-generated practice Numerical value Easy

A charge of 2 μC moves with a speed of 5 × 10³ m/s perpendicular to a uniform magnetic field of 0.4 T. If the force on it is x × 10^-3 N, find x.

Q16. AI-generated practice Numerical value Medium

A particle of mass 2 × 10^-26 kg and charge 1 × 10^-18 C moves with speed 2 × 10⁵ m/s perpendicular to a uniform magnetic field of 0.1 T. Find the radius of its path in cm.

Q17. AI-generated practice Numerical value Medium

In a velocity selector, the electric field is 6 × 10³ V/m and the magnetic field is 0.03 T, perpendicular to each other. If the speed of the undeflected particles is x × 10⁵ m/s, find x.

Q18. AI-generated practice Numerical value Hard

A proton enters a region of uniform magnetic field of width 5 cm, moving perpendicular both to the field and to the boundary of the region. Inside the field the radius of its circular path would be 10 cm. Find the angle (in degrees) through which the proton is deviated when it leaves the field region.

Q19. AI-generated practice Assertion–Reason Medium

Assertion (A): The kinetic energy of a charged particle moving in a uniform magnetic field remains constant.
Reason (R): The magnitude of the magnetic force on a moving charge is proportional to its charge.

A
Both A and R are true and R is the correct explanation of A
B
Both A and R are true but R is not the correct explanation of A
C
A is true but R is false
D
A is false but R is true

Q20. AI-generated practice Assertion–Reason Hard

Assertion (A): The time period of revolution of a charged particle in a uniform magnetic field is independent of its speed.
Reason (R): The radius of the circular path of the particle does not depend on its speed.

A
Both A and R are true and R is the correct explanation of A
B
Both A and R are true but R is not the correct explanation of A
C
A is true but R is false
D
A is false but R is true