Solenoid and Bar Magnet Analogy - UNSOLVED PRACTICE SET

Q7. What is a solenoid? Describe the magnetic field pattern produced by a current-carrying solenoid, both inside and outside.

Q8. Explain the similarity between the magnetic field of a current-carrying solenoid and that of a bar magnet. In what way is the solenoid's field 'better' for certain applications?

Q9. How can the north and south poles of a current-carrying solenoid be determined? Relate this to the Right Hand Thumb Rule.

Q10. What is an electromagnet? How is it different from a solenoid with an air core? Why is soft iron used rather than steel?

Q11. List three factors that affect the strength of an electromagnet and state how each factor influences the strength.

Q12. An electric bell uses an electromagnet. Briefly explain (in 2-3 sentences) how the electromagnet's on/off nature is used to produce the ringing sound.

Q13. Explain the magnetic field of a current-carrying solenoid and its analogy with a bar magnet in detail. Your answer must cover:
(a) the construction of a solenoid (description),
(b) the field pattern inside the solenoid (strong, uniform, parallel to axis) and outside (similar to a bar magnet),
(c) how to identify the north and south poles of the solenoid using the Right Hand Thumb Rule (curl the fingers in the direction of current; thumb points to N pole),
(d) why a uniform field exists inside but field lines diverge outside, similar to a bar magnet, and
(e) one practical advantage a solenoid has over a permanent bar magnet of the same strength.

Q14. Electromagnetic cranes are used at Indian ports (e.g., Jawaharlal Nehru Port, Mumbai) to lift scrap metal and shipping containers.
(a) Explain the working principle of an electromagnetic crane using the concept of a solenoid with a soft iron core.
(b) Why is soft iron used instead of permanent magnet steel for the core?
(c) List three ways the crane operator could increase the lifting power of the electromagnet.
(d) Explain what happens to the lifted scrap metal when the operator switches off the current.
(e) Why would a permanent magnet NOT be suitable for this application?

Q15. Compare the magnetic field of a single circular loop, a solenoid, and a bar magnet. Your answer must cover:
(a) describe the field pattern for each of the three,
(b) explain how a solenoid can be thought of as 'many circular loops stacked together' and how this affects field strength and uniformity,
(c) at what points (inside/outside/near poles) does the solenoid's field most resemble a bar magnet's field,
(d) why the field inside a solenoid is much more uniform than the field near a bar magnet's poles, and
(e) give one application each where
(i) a simple loop,
(ii) a solenoid, and 

(iii) a bar magnet would be the most appropriate choice.

Q16. A solenoid is wound such that, when viewed from one end, the current flows in a clockwise direction (as seen by the observer looking along the axis toward the solenoid).

(a) Using the Right Hand Thumb Rule (curl fingers in direction of current flow around the loops, thumb gives N pole direction), determine whether the end facing the observer is the North or South pole.
(b) If the current direction is reversed, what happens to the poles of the solenoid?
(c) If this solenoid is brought near a freely suspended bar magnet with its (determined) North pole facing the bar magnet's North pole, what will happen — attraction or repulsion? Explain.

Q17. An electromagnet is made by winding 200 turns of wire around a soft iron core and connecting it to a 6 V battery, producing a certain lifting force F.
(a) If the number of turns is increased to 400 (same current and core), how does the lifting force change qualitatively?
(b) If the current is doubled instead (turns unchanged), how does the force change?
(c) If the soft iron core is removed and replaced with air (same turns and current), how does the force change, and why?
(d) A factory wants to lift heavier loads — suggest two modifications to the electromagnet design to achieve this.

Q18. An electromagnet is made by winding 200 turns of wire around a soft iron core and connecting it to a 6 V battery, producing a certain lifting force F.
(a) If the number of turns is increased to 400 (same current and core), how does the lifting force change qualitatively?
(b) If the current is doubled instead (turns unchanged), how does the force change?
(c) If the soft iron core is removed and replaced with air (same turns and current), how does the force change, and why?
(d) A factory wants to lift heavier loads — suggest two modifications to the electromagnet design to achieve this.