📘 Chapter 8: Magnetism – Constructed Response Questions
Prepared by Muhammad Tayyab, Subject Specialist Physics, Govt Christian High School Daska. Based on PECTAA 2026 syllabus (National Curriculum 2023).
📖 What's Inside: This section covers constructed response questions from Chapter 8 Magnetism including Magnet Storage (Keepers), Solenoid Magnetization, Neutral Point, Electromagnetic Induction, and Magnetic Field Cancellation in Solenoids. Each question is presented with a detailed answer as per the official PECTAA 2026 Physics curriculum. Perfect for Punjab Boards (Lahore, Gujranwala, Multan, etc.) and all BISE boards across Pakistan.
📚 Related Resources – Chapter 8: Magnetism
Magnetism covers magnetic materials, magnetic fields, electromagnets, electromagnetic induction, and applications.
📖 Constructed Response Questions & Answers (PECTAA 2026)
8.1 Two bar magnets are stored in a wooden box. Label the poles of the magnets and identify P and Q objects.
Answer:
Labeling Poles:
- Left magnet: Top is \(N\)-pole, Bottom is \(S\)-pole.
- Right magnet: Top is \(S\)-pole, Bottom is \(N\)-pole.
Identification of P and Q: \(P\) and \(Q\) are soft iron keepers (soft magnetic materials) placed across the ends to form closed magnetic loops and preserve magnetization.
✅ P and Q are soft iron keepers that form closed magnetic loops to preserve magnetization
8.2 A steel bar has to be magnetised by placing it inside a solenoid such that end A of a bar becomes N-pole and end B becomes S-pole. Draw circuit diagram of solenoid showing steel bar inside it.
Answer:
The circuit diagram shows a steel bar placed inside a solenoid connected to a DC battery. The direction of current is such that end A becomes the N-pole and end B becomes the S-pole.
Figure: Steel bar magnetized inside a solenoid – End A becomes N-pole, End B becomes S-pole
✅ Current direction determines polarity: End A (N-pole), End B (S-pole)
8.3 Two bar magnets are lying as shown in the figure. A compass is placed at the middle of the gap. Its needle settles in the north-south direction. Label N and S poles of the magnets. Justify your answer by drawing fields lines.
Answer:
Figure: Neutral point – compass needle settles in N-S direction due to field cancellation
The compass needle points normally N-S because the magnetic fields of the two magnets cancel each other exactly at that point (called a neutral point).
This happens only when like poles face each other across the gap (both N or both S) — since like poles repel, their field lines push against each other from opposite sides and cancel out, leaving only Earth's field to act on the compass.
✅ Neutral point occurs when like poles face each other and their fields cancel out
8.4 Electric current or motion of electrons produce magnetic field. Is the reverse process true, that is the magnetic field gives rise to electric current? If yes, give an example and describe it briefly.
Answer:
Yes! This is called electromagnetic induction.
Example: In an AC generator, spinning a coil inside a magnet's field creates electric current in the coil.
✅ Electromagnetic induction – changing magnetic field induces electric current
8.5 Four similar solenoids are placed in a circle as shown in the figure. The magnitude of current in all of them should be the same. Show by diagram, the direction of current in each solenoid such that when current in anyone solenoid is switched OFF, the net magnetic field at the centre O is directed towards that solenoid. Explain your answer.
Answer:
Figure: Four solenoids arranged in a circle around center O
Wind each solenoid so its magnetic field at the center points away from itself (outward).
When all 4 are ON, their fields cancel each other out evenly.
When you switch one OFF, the balance breaks and the field left over at the center points toward the switched-off solenoid.
✅ All ON → fields cancel | One OFF → net field points toward switched-off solenoid
📐 Key Concepts – Magnetism (Constructed Response)
Keepers: Soft iron pieces that preserve magnetization
Solenoid: Coil producing field similar to bar magnet
Neutral Point: Point where fields cancel out
Electromagnetic Induction: Magnetic field → electric current
Field Cancellation: Symmetric solenoid arrangement cancels fields
💡 Exam Tip:
For constructed response questions, write detailed answers with clear reasoning and diagrams where required. Use the Right Hand Grip Rule to determine polarity of solenoids. These questions test your analytical and problem-solving skills. These questions follow the PECTAA 2026 pattern and are prepared by Subject Specialist Muhammad Tayyab.
Chapter 1Physical Quantities and Measurements
Chapter 2Kinematics
Chapter 3Dynamics
Chapter 4Turning Effect of Forces
Chapter 5Work and Energy
Chapter 6Mechanical Properties of Matter
Chapter 7Thermal Properties of Matter
Chapter 8✨ Magnetism
Chapter 9Nature of Science
📖 Complete syllabus coverage for Class 9 Physics (PECTAA 2026) – Chapters 1 to 9
Created by Hira Science Academy | Aligned with PECTAA 2026 Syllabus