Field Due to Coil/Solenoid MCQs Quiz | Class 10

This quiz on Field Due to Coil/Solenoid MCQs for Class X Science (Code 086), Unit IV: Effects of Current, covers essential concepts like the magnetic field of a solenoid and the principles of electromagnets. Test your understanding by attempting these questions. Once you complete the quiz, click ‘Submit Quiz’ to see your results and ‘Download Answer PDF’ to save your performance and review the correct answers.

Understanding Magnetic Field Due to Coil/Solenoid and Electromagnets

This section provides a detailed explanation of the concepts covered in the quiz, focusing on the magnetic fields produced by current-carrying coils, specifically solenoids, and the working principle of electromagnets. These topics are fundamental to understanding the practical applications of electricity and magnetism.

Magnetic Field Due to a Solenoid

A solenoid is a long coil of wire containing a large number of close turns, usually in the shape of a cylinder. When an electric current passes through a solenoid, it produces a magnetic field. The key characteristics of this field are:

  • Inside the Solenoid: The magnetic field lines inside a current-carrying solenoid are nearly parallel to the axis of the solenoid. This indicates that the magnetic field is uniform and strong within the solenoid.
  • Outside the Solenoid: The magnetic field lines outside a solenoid resemble those of a bar magnet. One end of the solenoid acts as a North pole and the other end as a South pole.
  • Direction of Field: The direction of the magnetic field can be determined using the Right-Hand Thumb Rule. If you curl the fingers of your right hand in the direction of the current flow around the solenoid, your outstretched thumb will point in the direction of the North pole.
  • Strength of Field: The strength of the magnetic field inside a solenoid is directly proportional to:
    • The number of turns per unit length of the solenoid.
    • The current flowing through the solenoid.
    • The nature of the core material (e.g., using a soft iron core significantly increases the field strength).

The Idea of an Electromagnet

An electromagnet is a temporary magnet that produces a magnetic field only when an electric current passes through it. It typically consists of a coil of insulated wire wound around a core of ferromagnetic material, usually soft iron.

  • Construction: A common electromagnet setup involves wrapping a coil of wire around a soft iron core.
  • Principle: When current flows through the coil, the magnetic field produced by the coil magnetizes the soft iron core. The soft iron core then greatly enhances the total magnetic field.
  • Why Soft Iron Core? Soft iron is used because it can be easily magnetized when current flows and can be quickly demagnetized when the current is switched off. This property makes it ideal for applications where the magnetic field needs to be turned on and off or its strength needs to be varied.
  • Controllability: The strength of an electromagnet can be controlled by:
    • Changing the current flowing through the coil.
    • Varying the number of turns in the coil.
    • Changing the core material.

Electromagnets vs. Permanent Magnets

Here’s a comparison highlighting the key differences:

Feature Electromagnet Permanent Magnet
Magnetism Temporary (active when current flows) Permanent
Strength Can be varied (by current, turns, core) Fixed
Polarity Can be reversed (by reversing current) Fixed
On/Off Control Can be switched on or off Cannot be switched off
Core Typically soft iron Hard steel or alloys

Quick Revision

  • A solenoid creates a uniform magnetic field inside and acts like a bar magnet outside.
  • The magnetic field strength of a solenoid depends on current, number of turns, and core material.
  • Right-Hand Thumb Rule determines the direction of poles for a solenoid.
  • Electromagnets are temporary magnets whose strength and polarity can be controlled.
  • Soft iron is used as an electromagnet core due to its easy magnetization and demagnetization.
  • Electromagnets are used in devices like electric bells, relays, and lifting cranes.

Extra Practice Questions

Test your understanding further with these questions:

  1. The magnetic field produced by a current-carrying solenoid is similar to that of:
    1. A horseshoe magnet
    2. A bar magnet
    3. A disc magnet
    4. A U-shaped magnet

    Answer: b) A bar magnet

  2. Which of the following will NOT increase the strength of an electromagnet?
    1. Increasing the current
    2. Increasing the number of turns in the coil
    3. Decreasing the length of the wire
    4. Using a soft iron core

    Answer: c) Decreasing the length of the wire

  3. The core of an electromagnet is made of soft iron because soft iron has:
    1. High retentivity and high coercivity
    2. Low retentivity and low coercivity
    3. High retentivity and low coercivity
    4. Low retentivity and high coercivity

    Answer: b) Low retentivity and low coercivity (meaning it can be easily magnetized and demagnetized)

  4. If the direction of current in a solenoid is reversed, the direction of its magnetic field:
    1. Remains the same
    2. Reverses
    3. Becomes zero
    4. Becomes perpendicular to the axis

    Answer: b) Reverses

  5. Which device does NOT typically use an electromagnet?
    1. Electric bell
    2. Loudspeaker
    3. Electric motor
    4. Simple compass

    Answer: d) Simple compass