9th Class Physics Notes 2026 – Chapter 8
Class 9 Physics Notes – Chapter 8: Magnetism
Board: Punjab Board
Subject: Physics
Class: 9th
Chapter: 8
A. Multiple Choice Questions
8.1. Which one of the following is not a magnetic material?
(a) Cobalt
(b) Iron
(c) Aluminium
(d) Nickel
Correct Answer: (c) Aluminium
Explanation: Aluminium is non-ferromagnetic, whereas cobalt, iron, and nickel are ferromagnetic materials.
8.2. Magnetic lines of force:
(a) Are always directed in a straight line
(b) Cross one another
(c) Enter into the north pole
(d) Enter into the south pole
Correct Answer: (d) Enter into the south pole
Explanation: Magnetic field lines emerge from the north pole and enter the south pole outside the magnet.
8.3. Permanent magnets cannot be made by:
(a) Soft iron
(b) Steel
(c) Neodymium
(d) Alnico
Correct Answer: (a) Soft iron
Explanation: Soft iron is easily magnetized and demagnetized, making it ideal for temporary magnets and electromagnets rather than permanent magnets.
8.4. Permanent magnets are used in:
(a) Circuit breaker
(b) Loudspeaker
(c) Electric crane
(d) Magnetic recording
Correct Answer: (b) Loudspeaker
Explanation: Loudspeakers use permanent magnets in their voice-coil assemblies to convert electrical signals into sound.
8.5. A common method used to magnetize a material is:
(a) Stroking
(b) Hitting
(c) Heating
(d) Placing inside a solenoid having AC
Correct Answer: (a) Stroking
Explanation: Stroking a magnetic material with a permanent magnet aligns its internal magnetic domains.
8.6. A magnetic compass is placed around a bar magnet at four points, as shown in the figure. Which diagram would indicate the correct directions of the field?
(a) Diagram (a)
(b) Diagram (b)
(c) Diagram (c)
(d) Diagram (d)
Correct Answer: (b) Diagram (b)
Explanation: Compass needles align along magnetic field lines, which are directed away from the north pole and towards the south pole outside the magnet.
Note: The original diagrams were not provided, so the selected option is retained from the supplied source.
8.7. A steel rod is magnetized by the double-touch stroking method. Which one would be the correct polarity of the AB magnet?
(a) Diagram (a)
(b) Diagram (b)
(c) Diagram (c)
(d) Diagram (d)
Correct Answer: (c) Diagram (c)
Explanation: In double-touch stroking from the centre outward, the poles produced at the ends depend on the poles of the magnets used for stroking.
Note: The original diagrams were not provided, so the selected option is retained from the supplied source.
8.8. The best material to protect a device from an external magnetic field is:
(a) Wood
(b) Plastic
(c) Steel
(d) Soft iron
Correct Answer: (d) Soft iron
Explanation: Soft iron has high magnetic permeability and acts as a magnetic shield by diverting magnetic field lines around the protected space.
B. Short Answer Questions
8.1. What are temporary and permanent magnets?
Answer:
Temporary magnets: Made of soft magnetic materials, such as soft iron, that retain magnetism only while an external magnetic field is present.
Permanent magnets: Made of hard magnetic materials, such as steel, alnico, and neodymium, that retain their magnetism for a long time after being magnetized.
8.2. Define the magnetic field of a magnet.
Answer: The magnetic field is the region around a magnet where its magnetic force can be experienced by other magnets or magnetic materials.
8.3. What are magnetic lines of force?
Answer: Magnetic lines of force are imaginary continuous lines used to visualize the direction and strength of a magnetic field. Outside a magnet, they point from the north pole to the south pole.
8.4. Name some uses of permanent magnets and electromagnets.
Answer:
Permanent magnets: Used in loudspeakers, electric motors, compasses, and refrigerator door seals.
Electromagnets: Used in electric bells, relays, magnetic cranes, and particle accelerators.
8.5. What are magnetic domains?
Answer: Magnetic domains are microscopic regions within a magnetic material where the magnetic moments of atoms are aligned in the same direction due to quantum exchange interactions.
8.6. Which type of magnetic field is formed by a current-carrying long coil?
Answer: A current-carrying long coil produces a uniform magnetic field directed along the axis of the coil, similar to the magnetic field of a bar magnet.
8.7. Differentiate between paramagnetic and diamagnetic materials.
Answer:
Paramagnetic materials: Weakly attracted by a magnet. Their atoms possess net magnetic moments. Examples include aluminium and platinum.
Diamagnetic materials: Weakly repelled by a magnet. Their induced magnetic moment opposes the external field. Examples include copper and bismuth.
C. Constructed Response Questions
8.1. Two bar magnets are stored in a wooden box. Label the poles of the magnets and identify objects P and Q.
Answer: When bar magnets are stored in pairs, opposite poles must face each other. Soft iron keepers (P and Q) are placed across the ends to form closed magnetic loops and prevent self-demagnetization.
Note: The original figure was not provided, so the exact labels and positions of P and Q cannot be confirmed.
8.2. A steel bar has to be magnetized by placing it inside a solenoid such that end A of the bar becomes a north pole and end B becomes a south pole. Draw a circuit diagram of the solenoid showing the steel bar inside it.
Answer: To make end A a north pole and end B a south pole, direct DC current through the solenoid so that, when viewed from end A, the current flows in a counterclockwise direction, according to the right-hand grip rule.
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 the N and S poles of the magnets. Justify your answer by drawing field lines.
Answer: For the compass needle to settle neutrally between the magnets, like poles—either two north poles or two south poles—must face each other, creating a zero-field neutral point at the centre.
Note: The original figure was not provided, so the exact pole labels cannot be confirmed.
8.4. Electric current or motion of electrons produces a magnetic field. Is the reverse process true, that is, does a magnetic field give rise to electric current? If yes, give an example and describe it briefly.
Answer: Yes. This process is called electromagnetic induction, described by Faraday’s law.
For example, moving a bar magnet in and out of a closed wire coil induces an electric current in the coil.
8.5. Four similar solenoids are placed in a circle, as shown in the figure. Show by diagram the direction of current in each solenoid such that when the current in any one solenoid is switched off, the net magnetic field at the centre O is directed towards that solenoid. Explain your answer.
Answer: The resultant magnetic field depends on the vector sum of the magnetic fields produced by the solenoids. The current directions must be arranged so that switching off one solenoid leaves a resultant field directed towards that solenoid.
Note: The original figure and solenoid arrangement were not provided. The exact current directions cannot be determined from the supplied text alone.
D. Comprehensive Questions
8.1. How can you identify whether an object is a magnet or a magnetic material?
Answer: Repulsion is the sure test of a magnet. A magnet attracts an unmagnetized magnetic material, but it can repel a like pole of another magnet.
8.2. Describe the strength of a magnetic field in terms of magnetic lines of force. Explain it by drawing a few diagrams for the fields as examples.
Answer: Magnetic field strength is proportional to the density, or closeness, of magnetic field lines. Closely spaced lines indicate a stronger magnetic field, such as near the poles of a bar magnet.
8.3. What is a circuit breaker? Describe its working with the help of a diagram.
Answer: A circuit breaker is an automatic safety switch that interrupts the current during an overload. It uses an electromagnet or a bimetallic strip, which pulls open a latch to separate the circuit contacts.
8.4. “A magnet attracts only a magnet.” Explain the statement.
Answer: True attraction between two magnets occurs when opposite poles face each other. When a magnet attracts an unmagnetized iron piece, it induces temporary opposite polarity in the iron, so it attracts the induced magnetic pole.
8.5. Differentiate between paramagnetic, diamagnetic, and ferromagnetic materials with reference to the domain theory.
Answer:
Diamagnetic materials: According to the supplied source, they have no unpaired electrons and no magnetic domains; they are weakly repelled by a magnetic field.
Paramagnetic materials: Their atomic dipoles align weakly with an external magnetic field, resulting in weak attraction.
Ferromagnetic materials: They contain large magnetic domains that align strongly in an external magnetic field and can retain their alignment.
8.6. Why are ferromagnetic materials suitable for making magnets?
Answer: Ferromagnetic materials possess strong magnetic domains that easily align in an external magnetic field and retain their alignment after the field is removed, forming strong permanent magnets.
Notes by Sir Dilawar
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