Magnetic Effect of Electric Current Class 10 || Science|| Chapter 12 Notes

Magnetic Effects of Electric Current Class 10 ||Science|| Chapter 12 Notes

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1. Introduction

Electric current not only produces heating effects but also produces magnetic effects. This phenomenon is called the magnetic effect of electric current. The study of this effect reveals that a current-carrying conductor generates a magnetic field around it, which can influence magnetic materials or other conductors.

2. Magnetic Field and Field Lines

• Magnetic Field: The region around a magnetic material or a current-carrying conductor where its magnetic force can be experienced is called the magnetic field.
• Magnetic Field Lines: These are imaginary lines used to represent the strength and direction of a magnetic field.
  • The field lines emerge from the north pole and merge at the south pole of a magnet.
  • The closer the field lines, the stronger the magnetic field.
  • Magnetic field lines never intersect.

Properties of Magnetic Field Lines:

1. They form closed loops from the north to the south pole.
2. The direction of field lines inside the magnet is from the south to the north pole.
3. The strength of the magnetic field is greater where the lines are closer.

3. Magnetic Field Due to a Current-Carrying Conductor

Magnetic Field Around a Straight Conductor:

When electric current flows through a straight conductor (e.g., a wire), a magnetic field is produced around it. This field consists of concentric circles centered on the wire.

• The direction of the magnetic field can be determined using the Right-Hand Thumb Rule.

Right-Hand Thumb Rule:

• If you hold a current-carrying conductor in your right hand such that your thumb points in the direction of current flow, then the direction in which your fingers curl gives the direction of the magnetic field.

Magnetic Field Due to a Circular Loop:

• The magnetic field produced by a current-carrying circular loop is similar to that of a bar magnet, with the field lines resembling closed loops.
• At the center of the loop, the magnetic field is perpendicular to the plane of the loop.

Magnetic Field Due to a Solenoid:

• A solenoid is a coil of wire with many turns. When electric current passes through it, it produces a magnetic field similar to a bar magnet, with a distinct north and south pole.
• The magnetic field inside a solenoid is uniform and strong, whereas outside, it is weak.
• A solenoid can be used to magnetize a piece of magnetic material like iron, turning it into an electromagnet.

4. Electromagnet and Its Uses

• An electromagnet is formed when a soft iron core is placed inside a solenoid and current is passed through it.
• Electromagnets are widely used in:
  • Electric bells
  • Loudspeakers
  • Cranes to lift heavy iron objects
  • MRI machines in hospitals

5. Force on a Current-Carrying Conductor in a Magnetic Field

When a current-carrying conductor is placed in a magnetic field, it experiences a force. The direction of this force depends on:

• The direction of the current.
• The direction of the magnetic field.

Fleming’s Left-Hand Rule:

• Hold your left hand such that your thumb, forefinger, and middle finger are perpendicular to each other.
  • The forefinger points in the direction of the magnetic field.
  • The middle finger points in the direction of current.
  • The thumb gives the direction of the force experienced by the conductor.

This principle is used in electric motors, where the force exerted on a current-carrying conductor placed in a magnetic field produces rotational motion.

6. Electric Motor

An electric motor is a device that converts electrical energy into mechanical energy. It works on the principle of the magnetic effect of electric current. When current flows through the armature of a motor placed in a magnetic field, it experiences a force, causing the armature to rotate.

Working of a Simple Electric Motor:

1. A rectangular coil is placed between the poles of a permanent magnet.
2. When current flows through the coil, a magnetic field is created around it.
3. The forces on opposite sides of the coil are in opposite directions, causing the coil to rotate.
4. A commutator reverses the direction of current in the coil, ensuring continuous rotation.

7. Electromagnetic Induction

Electromagnetic Induction is the process by which a changing magnetic field induces an electric current in a conductor. This phenomenon was discovered by Michael Faraday.

Faraday’s Experiments:

Faraday observed that when the magnetic field around a conductor changes, an electric current is induced in the conductor. This process is called electromagnetic induction.

Fleming’s Right-Hand Rule:

• Hold your right hand such that your thumb, forefinger, and middle finger are perpendicular to each other.
  • The forefinger points in the direction of the magnetic field.
  • The thumb points in the direction of motion of the conductor.
  • The middle finger gives the direction of the induced current.

8. Electric Generator

An electric generator converts mechanical energy into electrical energy by electromagnetic induction. It operates on the principle of inducing a current by rotating a coil within a magnetic field.

Working of an Electric Generator:

1. A rectangular coil is rotated between the poles of a magnet.
2. As the coil rotates, the magnetic field through the coil changes, inducing an electric current.
3. The current direction changes every half rotation, producing alternating current (AC).

In some generators, a split-ring commutator is used to produce direct current (DC).

9. Domestic Electric Circuits

In household wiring, electrical energy is supplied to homes via the main supply. Key components of a domestic circuit include:

1. Live Wire (Positive) – Red in color.
2. Neutral Wire (Negative) – Black in color.
3. Earth Wire – Green in color; used for safety to prevent shocks.

Safety devices like fuses and circuit breakers protect the circuit from overloads or short circuits.

10. Key Concepts:

• Magnetic effect of electric current: A current-carrying conductor generates a magnetic field.
• Right-Hand Thumb Rule: Determines the direction of the magnetic field around a current-carrying conductor.
• Fleming’s Left-Hand Rule: Determines the direction of force on a current-carrying conductor in a magnetic field.
• Electromagnetic Induction: Inducing electric current in a conductor by changing its magnetic environment.
• Fleming’s Right-Hand Rule: Determines the direction of induced current.
• Electric Motor: Converts electrical energy into mechanical energy.
• Electric Generator: Converts mechanical energy into electrical energy.

Summary:

• Electric current produces a magnetic field, which can be used to create electromagnets and operate electric motors.
• Magnetic fields interact with current-carrying conductors to produce force, which is the basis of motor action.
• The phenomenon of electromagnetic induction is used in generators to convert mechanical energy into electrical energy.
• Household circuits rely on alternating current (AC), with proper wiring and safety devices to prevent accidents.

These principles are foundational to many devices and technologies used in daily life, from household appliances to industrial machinery.