(a) What is an electromagnet? List any two uses.

(b) Draw a labelled diagram to show how an electromagnet is made.

(c) State the purpose of soft iron core used in making an electromagnet.

(d) List two ways of increasing the strength of an electromagnet if the material of the electromagnet is fixed.

Q: (a) What is an electromagnet? List any two uses. (b) Draw a labelled diagram to show how an electromagnet is made. (c) State the purpose of soft iron core used in making an electromagnet. (d) List two ways of increasing the strength of an electromagnet if the material of the electromagnet is fixed.

(a) **Electromagnet**: A temporary magnet formed when a piece of magnetic material, like soft iron, is placed inside a current-carrying solenoid coil and becomes magnetised by the strong magnetic field produced inside the solenoid. **Two uses**: 1. Used in electric motors, loudspeakers, and microphones. 2. Used in industrial cranes to lift and transport heavy iron scrap and machinery. (b) **Labelled Diagram**: ```diagram {"xrange": [76.0, 324.0], "yrange": [-222.0, -98.0], "polygons": [{"points": [[100.0, -110.0], [300.0, -110.0], [300.0, -140.0], [100.0, -140.0]]}, {"points": [[160.0, -190.0], [200.0, -190.0], [200.0, -210.0], [160.0, -210.0]]}], "lines": [{"from": [100.0, -125.0], "to": [100.0, -200.0], "label": ""}, {"from": [300.0, -125.0], "to": [300.0, -200.0], "label": ""}, {"from": [100.0, -200.0], "to": [160.0, -200.0], "label": ""}, {"from": [240.0, -200.0], "to": [300.0, -200.0], "label": ""}], "points": [{"x": 200.0, "y": -125.0, "label": "Soft Iron Core"}, {"x": 180.0, "y": -200.0, "label": "Battery"}, {"x": 220.0, "y": -200.0, "label": "Key (K)"}]} ``` (c) **Purpose of Soft Iron Core**: 1. It has high magnetic permeability, which concentrates and greatly intensifies the magnetic field lines inside the solenoid, making the electromagnet much stronger. 2. It is a temporary magnetic material, meaning it loses almost all of its magnetism as soon as the electric current is switched off, allowing the electromagnet to be turned on and off at will. (d) **Two ways to increase the strength of the electromagnet**: 1. **By increasing the current ($I$)** flowing through the solenoid coil. 2. **By increasing the number of turns ($n$)** per unit length of the solenoid coil.

Magnetic Effects of Electric Current

Electromagnet

Official Answer

(a) Electromagnet: A temporary magnet formed when a piece of magnetic material, like soft iron, is placed inside a current-carrying solenoid coil and becomes magnetised by the strong magnetic field produced inside the solenoid.

Two uses:

Used in electric motors, loudspeakers, and microphones.
Used in industrial cranes to lift and transport heavy iron scrap and machinery.

(b) Labelled Diagram:

It has high magnetic permeability, which concentrates and greatly intensifies the magnetic field lines inside the solenoid, making the electromagnet much stronger.
It is a temporary magnetic material, meaning it loses almost all of its magnetism as soon as the electric current is switched off, allowing the electromagnet to be turned on and off at will.

(d) Two ways to increase the strength of the electromagnet:

By increasing the current ( $I$ ) flowing through the solenoid coil.
By increasing the number of turns ( $n$ ) per unit length of the solenoid coil.

ElectromagnetSoft iron coreSolenoidBatteryCurrentNumber of turnsTemporary magnet

Marking Scheme

11 Mark: Definition of electromagnet and two uses.
21.5 Marks: Labelled diagram showing solenoid, soft iron core, battery, and key.
31 Mark: Explaining the purpose of the soft iron core (high permeability and temporary magnetism).
41.5 Marks: Listing two ways to increase strength (increasing current and increasing number of turns).

Hint

Recall how a solenoid can be used to magnetise a soft iron core. Think about the factors that affect the magnetic field of a solenoid: current and number of turns.

Quick Oral Answer

An electromagnet is a temporary magnet made by winding a coil of insulated copper wire around a soft iron core. When current passes through the coil, it becomes magnetised. Its strength can be increased by increasing the current or the number of turns in the coil.

Analysis & Explanation

An electromagnet is a temporary magnet whose magnetic field is produced by an electric current. The core of the electromagnet is made of soft iron because soft iron magnetises easily when current is passed and demagnetises completely when current is stopped. The strength of the magnetic field ( $B$ ) inside a solenoid is directly proportional to the current ( $I$ ) and the number of turns per unit length ( $n$ ), i.e., $B \propto nI$ .

Common Mistakes

1Using steel instead of soft iron for the core (steel retains magnetism and becomes a permanent magnet, which is undesirable for an electromagnet).
2Forgetting to label the battery polarity or the key in the diagram.

Interesting Facts

Electromagnets are so powerful that they are used in Maglev (magnetic levitation) trains to suspend and propel the train at high speeds without any mechanical contact!

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Frequently Asked Questions

How many marks does this question carry in CBSE Class 10 Science 2020?

This question carries 5 marks in the CBSE Class 10 Science 2020 examination.

Which chapter does this question come from in Science?

This question is from the chapter "Magnetic Effects of Electric Current" in the CBSE Class 10 Science syllabus.

What topic does this question cover in Science?

This question covers the topic "Electromagnet" from CBSE Class 10 Science.

What type of question is this in the CBSE Class 10 Science 2020 paper?

This is a Long Answer question from Section C in the CBSE Class 10 Science 2020 paper.