Bar Magnet as an Equivalent Solenoid - UNSOLVED PRACTICE SET
Chapter: Magnetism and Matter | Topic: Bar Magnet as an Equivalent Solenoid
BAR MAGNET AS AN EQUIVALENT SOLENOID - UNSOLVED PRACTICE SET
Topic: Bar Magnet as an Equivalent Solenoid
Multiple Choice Questions
Q1. A current-carrying solenoid behaves like a bar magnet because:
- It produces electric charge at its ends
- The current loops create a net magnetic dipole moment
- It generates heat at the poles
- It becomes permanently magnetized
Q2. The north pole of a current-carrying solenoid is determined by:
- The length of the solenoid
- The direction of current flow (right-hand rule)
- The material of the solenoid
- The number of layers of winding
Q3. The magnetic field inside a long solenoid carrying current is:
- Zero
- Uniform and parallel to the axis
- Non-uniform and radial
- Maximum at the centre and zero at the ends
Q(d) Maximum at the centre and zero at the ends
4. A solenoid with N turns, length L, and current I has a magnetic moment proportional to:
- N/L
- N × I × L
- N × I × A (where A is cross-sectional area)
- I/L
Q5. If the current in a solenoid is reversed, its magnetic field pattern:
- Disappears completely
- Remains unchanged
- Reverses direction (north and south poles interchange)
- Becomes non-uniform
Q6. The magnetic field outside an ideal long solenoid is:
- Very strong
- Zero
- Equal to the field inside
- Perpendicular to the axis
Short Answer Questions
Q7. State Ampere's right-hand rule for a solenoid. How does it help in determining the polarity of the solenoid?
Q8. Why is a current-carrying solenoid considered equivalent to a bar magnet? Mention two similarities between them.
Q9. What happens to the magnetic field inside a solenoid if:
(a) The number of turns per unit length is doubled?
(b) The current is halved?
Q10. A student wraps a copper wire around a plastic tube to make a solenoid. Will it behave like a magnet when current passes through it? Explain.
Q11. How does the magnetic field pattern of a solenoid differ from that of a bar magnet when observed using iron filings?
Q12. Why does a solenoid lose its magnetic properties when the current is switched off, while a bar magnet retains them?
Long Answer Questions
Q13. Derive the expression for the magnetic field at a point on the axis of a long solenoid carrying current. Hence, explain why the field is uniform inside and weak outside.
Q14. Explain how a current-carrying solenoid can be considered as an arrangement of circular current loops. Use this to derive the expression for its magnetic dipole moment.
Q15. Compare and contrast a bar magnet and a current-carrying solenoid under the following heads:
(i) Origin of magnetism
(ii) Control over magnetic properties
(iii) Practical applications
Numerical & Application-Based Problems
Q16. A solenoid of length 50 cm has 400 turns and carries a current of 3 A. The cross-sectional area of the solenoid is 2 × 10⁻⁴ m².
(a) Calculate the magnetic field inside the solenoid.
(b) Find the magnetic dipole moment of the solenoid.
(c) If this solenoid is placed in a uniform magnetic field of 0.2 T perpendicular to its axis, calculate the torque acting on it.
Q17. A solenoid of 600 turns is wound uniformly over a length of 60 cm. A current of 4 A passes through it. The solenoid has a circular cross-section of radius 1.5 cm.
(a) Calculate the magnetic field at the centre of the solenoid.
(b) Determine the pole strength equivalent of this solenoid if it is to be compared with a bar magnet of length 60 cm.
(c) At what distance from the centre on the axial line would the magnetic field be one-eighth of its value at the centre?
Q18. In a school physics project, students are asked to build an electromagnet using a solenoid. Team A uses a solenoid with 300 turns, length 30 cm, radius 1 cm, and current 2 A. Team B suggests using a bar magnet of magnetic moment 1.5 Am² instead.
(a) Calculate the magnetic moment of Team A's solenoid.
(b) Compare the magnetic moments of both setups.
(c) Discuss one practical advantage of using the solenoid over the bar magnet in this project, and one situation where the bar magnet would be preferable.