Grade 9 Magnetic Fields
Grade 9 Independent Portfolio Work: Magnetic Fields
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QUESTION 1
- Scenario Introduction: Four metallic bars are suspended freely from a ceiling as illustrated in the accompanying diagram. The points of attachment for bars X and Y on the ceiling are separated by 4 cm. The distance between the two middle bars, which are bar magnets X and Y, is 5 cm. One of the outer bars, either A or B, is made of iron, while the other is made of gold.
1.1 Definition of Magnetic Material
- Term: Ferromagnetic material (2 marks).
- Explanation: A ferromagnetic material is easily magnetised, demonstrating strong magnetic properties and capable of becoming a permanent magnet under magnetic influence.1.2 Identification of Iron Bar
- Choice: Bar A is made of iron (2 marks).
- Justification: Iron is a ferromagnetic material known for its ability to be easily magnetised compared to gold, which is non-magnetic. Thus, given the properties of the two metals, bar A retains greater magnetic characteristics.1.3 Determination of Polarity
- Answer: NORTH (1 mark).
- Explanation: Since bar Y is a bar magnet and bar B is positioned at its vicinity, the closer end of bar B to bar Y acquires a north polarity to oppose the north pole of bar Y based on magnetic field interaction.1.4 Explanation of Polarity Determination
- Explanation: According to the principles of magnetism, like poles repel while opposite poles attract. The northern end of bar magnet Y causes the nearest end of bar B to become magnetically polarized as north, resulting in bar B evading bar Y as they are both north poles.1.5 Magnetic Field Sketch
- Task: Sketch the magnetic field pattern around bar magnet X (3 marks).
- Guidelines: Field lines should originate from the north pole of bar magnet X, arching in a loop, and terminating at its south pole, illustrating the magnetic field that influences surrounding space.
- Description of the sketch: Field lines indicating the strength and direction of the magnetic field, denoting density (more lines indicate stronger fields).
Total for QUESTION 1: 10 marks
QUESTION 2
- Scenario Introduction: Two magnets are aligned such that their north poles are facing each other.
2.1 Definition of Magnetic Field
- Definition: A magnetic field is a region around a magnet where magnetic forces can be observed and experienced (2 marks).2.2 Magnetic Field Pattern Drawing
- Task: Draw the magnetic field pattern between the two north poles of the magnets (3 marks).
- Guidelines: The field should illustrate repulsion where the lines do not converge between the two north poles.2.3 Analysis of Graph
- 2.3.1 Mathematical Relationship
- Statement of Relationship: As the distance between the magnets increases, the magnetic force decreases. This can often be represented as an inverse relationship; mathematically it can be seen as F ext{ is proportional to } rac{1}{d^2} (1 mark).
- 2.3.2 Magnitude of Magnetic Force
- Value: 0.3 N (2 marks).
- Explanation: Reading from the provided graph at a distance of 4 cm yields a force value of 0.3 N.
- 2.3.3 Distance for a Given Force
- Value: To experience a force of 0.05 N, the magnets need to be positioned at a distance of 8 cm apart (2 marks).
Total for QUESTION 2: 10 marks
QUESTION 3
- Scenario Introduction: The diagram shows the magnetic field lines between the two magnetic poles of a magnet.
3.1 Explanation of Non-Contact Forces
- 3.1.1 Definition of Non-Contact Force
- Definition: A non-contact force is a force that acts on an object without it being in physical contact (2 marks).
- 3.1.2 Example: Another example of a non-contact force is gravitational force (2 marks).3.2 Nature of the Force Between Two Poles
- Nature Statement: The nature of the force between two poles of a magnet, when like poles face each other, is repulsive (2 marks).3.3 Determination of Polarity
- Polarity Identification: The polarity of pole 2 is SOUTH (2 marks).
- Reason: Pole 2 must be south to also attract the north pole of another magnet.
Total for QUESTION 3: 8 marks
QUESTION 4
- Scenario Overview: Many everyday devices leverage electric and magnetic forces.
- 3 Examples of Magnetic Forces in Everyday Life
- Example 1: Magnetic compasses use Earth's magnetic field to indicate direction (2 marks).
- Example 2: Refrigerator magnets are used to hold notes or reminders on metal surfaces (2 marks).
- Example 3: Magnetic levitation trains use magnetic forces to lift and propel vehicles along tracks, allowing for high-speed travel (2 marks).