1. Electricity and Magnetism Connection:

  • In earlier chapters, we studied the heating effects of electric current. In this chapter, we explore other effects of electric current.
  • An important effect is the magnetic effect: an electric current flowing through a wire creates a magnetic field, making the wire behave like a magnet.

2. Experiment to Observe the Magnetic Effect:

  • Activity 12.1:
    • Place a copper wire in an electric circuit.
    • Put a compass near the wire, and observe the needle.
    • When current flows, the needle of the compass deflects, showing that the wire has produced a magnetic effect. This proves that electricity and magnetism are connected.

3. Hans Christian Oersted:

  • In 1820, Oersted discovered that an electric current can cause a compass needle to deflect, indicating a link between electricity and magnetism.
  • His discovery led to technologies like radio, television, and fiber optics, and the unit of magnetic field strength is named after him (Oersted).

4. Magnetic Field and Field Lines:

  • Compass and Magnet: A compass needle points in the north-south direction. When brought near a magnet, the compass needle gets deflected. The compass needle itself is a small magnet.
  • Magnetic Poles: Like poles (north-north or south-south) repel, and unlike poles (north-south) attract.

5. Understanding Magnetic Fields:

  • Activity 12.2:
    • Sprinkle iron filings around a bar magnet and tap the paper to see the filings align along the magnetic field lines.
  • Magnetic Field: The region around a magnet where its force can be detected is called the magnetic field. The pattern formed by the filings shows the magnetic field lines.
  • Magnetic Field Lines:
    • Magnetic field lines emerge from the north pole and enter the south pole of a magnet.
    • Field lines are closed curves, and the strength of the magnetic field is stronger where the lines are closer together.
    • Magnetic field lines never cross each other because a compass needle would point in two directions if they did.

6. Magnetic Field of a Current-Carrying Conductor:

  • Magnetic Field Due to Current: An electric current passing through a conductor (such as a copper wire) generates a magnetic field around it.
  • Direction of Magnetic Field: The direction of the magnetic field can be determined using the right-hand rule: If you hold the conductor with your right hand, your thumb points in the direction of current flow, and your fingers curl in the direction of the magnetic field.

7. Effect of Current and Distance on Magnetic Field:

  • Distance Effect: As the compass moves farther from the wire, the deflection decreases, showing that the magnetic field strength decreases with distance from the wire.
  • Magnetic field lines around a current-carrying wire form concentric circles that get larger as the distance from the wire increases.

Key Concepts for Competitive Exams:

  • Magnetic effect of current: An electric current produces a magnetic field.
  • Oersted’s Experiment: Demonstrated the relationship between electricity and magnetism.
  • Magnetic field lines: Visualize the magnetic field around magnets and current-carrying conductors.
  • Right-hand rule: Determines the direction of the magnetic field around a current-carrying wire.
  • Current and magnetic field strength: The magnetic field strength increases with the current and decreases with distance.

Right-Hand Thumb Rule

  • The right-hand thumb rule helps determine the direction of the magnetic field around a current-carrying conductor.
  • To apply the rule, hold the conductor with your right hand such that your thumb points in the direction of the current. Your fingers will then curl in the direction of the magnetic field.
  • The field lines are concentric circles around the wire.
  • If the direction of current is reversed, the direction of the magnetic field also reverses.

Magnetic Field of a Circular Loop

  • When a current passes through a circular loop, it creates concentric magnetic field lines, which get larger as they move away from the wire.
  • At the center of the loop, the magnetic field lines appear as straight lines.
  • All points on the wire contribute to a uniform magnetic field within the loop.

Magnetic Field of a Solenoid

  • A solenoid is a coil of many turns of wire and produces a strong, uniform magnetic field inside.
  • The magnetic field inside the solenoid is parallel, while outside, it is similar to the field around a bar magnet (with a north and south pole).
  • The magnetic field in a solenoid can be used to create an electromagnet by placing a soft iron core inside it.

Force on a Current-Carrying Conductor in a Magnetic Field

  • A current-carrying conductor experiences a force when placed in a magnetic field. The force depends on the direction of the current and the magnetic field.
  • Fleming’s Left-Hand Rule helps find the direction of the force:
    • The thumb points in the direction of the force.
    • The first finger points in the direction of the magnetic field.
    • The second finger points in the direction of the current.
  • The force is largest when the current is perpendicular to the magnetic field.

Domestic Electric Circuits

  • Household circuits use live, neutral, and earth wires.
    • Live wire (positive) is red, neutral wire (negative) is black, and the earth wire (safety) is green.
  • The voltage difference between the live and neutral wire is 220 V in most homes.
  • Appliances are connected in parallel, ensuring equal voltage across them.
  • An electric fuse protects circuits from overloading and short circuits by melting when the current exceeds safe limits.

Safety in Domestic Circuits

  • Earth wire ensures safety by providing a path for leakage current to the ground.
  • Overloading happens when the current exceeds the circuit’s limit, which could be due to connecting too many appliances or a short circuit.
  • The fuse prevents damage by breaking the circuit when overloading occurs.

Key Takeaways

  • A compass needle helps show the direction of the magnetic field.
  • A current-carrying wire produces a magnetic field, with the direction given by the right-hand rule.
  • The magnetic field around a solenoid is similar to that of a bar magnet, and solenoids can create electromagnets.
  • Force on a conductor in a magnetic field follows Fleming’s left-hand rule and is strongest when the current is perpendicular to the magnetic field.
  • Domestic circuits are protected by fuses and the earth wire for safety.

THERE ALL ARE THE NOTES OF CHAPTER 12. AND AFTER SOME TIME YOU GET IMPORTANT QUESTIONS AND DIAGRAMS HERE. *#THANKS FOR VISITING, VISIT AGAIN#* 😊