Answer key

Prepared by: learnloophq@gmail.com

Last edited 26 days ago by Learn LoopHQ.

Chapter: 07. Magnetism

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Section A: Multiple Choice Questions

c) Plastic ruler

b) At its two ends (poles)

b) They repel

c) Magnetic lines of force

c) An electromagnet when current is flowing

Section B: Fill in the Blanks

magnetite

north-south

Repulsion

north

turns

Section C: True/False

False

True

False

True

Section D: Short Answer Questions

A magnet is any substance that has the property of attracting materials like iron, steel, cobalt, and nickel. This property is known as magnetism.

Two examples of magnetic substances are iron nails and steel paper clips.

The magnetic axis is the imaginary straight line that joins the north and south poles of a magnet.

The Earth is considered a giant magnet because it has its own magnetic field, generated by the movement of molten metal in its core. This field causes freely suspended magnets to align north-south.

Two common uses of magnets are in magnetic compasses for finding directions and in refrigerator doors to keep them sealed.

Section E: Diagram-Based Question

a) The method of magnetisation shown in this diagram is the single touch method. b) If the rubbing magnet’s North pole is used and rubbed from X to Y, end X of the steel rod will acquire North polarity, and end Y will acquire South polarity.

Section F: Long Answer Questions

Permanent magnets retain their magnetic properties for a long time and are typically made of steel, with fixed north and south poles. Their strength is generally constant. Temporary magnets, on the other hand, only exhibit magnetic properties temporarily, often when an electric current is flowing through them or when near another magnet. They are usually made of soft iron, and their pole positions can change, and their strength can be varied.

Magnets should be stored properly using magnetic keepers to prevent demagnetization. For bar magnets, they should be stored in pairs with their opposite poles facing each other, separated by a piece of wood in between. Soft iron keepers should be placed across their ends to complete the magnetic circuit. A horseshoe or U-shaped magnet needs only one keeper placed across its poles. This proper storage helps preserve their magnetic strength over time.

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