Magnetic Effects of Electric Current & Domestic Circuits

The magnetic effect of electric current is one of the most important discoveries in physics. When an electric current flows through a conductor, it produces a magnetic field around it. This phenomenon forms the basis of electromagnetism and has several applications in our daily lives.

Properties of Magnetic Field Lines

• A magnetic field line is a closed and continuous curve.
• The strength of the magnetic field is expressed by the closeness of magnetic field lines. Closer lines indicate stronger fields.
• No two magnetic field lines intersect each other.
• Parallel and equidistant field lines represent a uniform magnetic field.

Magnetic Field Around a Straight Current-Carrying Conductor

• The field lines are concentric circles around the conductor.
• The strength of the field depends on:
  1. Amount of current flowing
  2. Distance from the conductor
  3. Direction of current

Right-Hand Thumb Rule

If the conductor is held with the right hand such that the thumb points in the direction of current, the fingers encircle the wire in the direction of the magnetic field.

Magnetic Field Due to a Circular Coil

• The magnetic field lines around a circular coil are concentric circles.
• The strength of the field at the center depends on:
  • Radius of the coil
  • Number of turns in the coil
  • Strength of current in the coil
• The direction of the field is determined by the Clock Rule.

Magnetic Field Produced by a Solenoid

A solenoid is a coil of many turns of insulated copper wire. When current passes through it, a uniform magnetic field is produced inside, similar to a bar magnet.

• One end acts as the North Pole, the other as the South Pole.
• The field strength depends on:
  1. Current flowing
  2. Number of turns per unit length
• A solenoid with a soft iron core becomes an Electromagnet.

Force on a Current-Carrying Conductor in a Magnetic Field

A conductor carrying current experiences a force when placed in a magnetic field.

Fleming’s Left Hand Rule

Stretch the thumb, forefinger, and middle finger of the left hand mutually perpendicular. The thumb gives the direction of force, the forefinger the direction of the magnetic field, and the middle finger the direction of current.

Electromagnetic Induction

Michael Faraday discovered that a changing magnetic field induces an electric current in a conductor. This is called Electromagnetic Induction.

Experiments

• Self-Induction: Moving a magnet towards or away from a coil induces current in the same coil.
• Mutual Induction: A change of current in one coil induces a current in a nearby coil.

Types of Current

• Alternating Current (AC): Changes direction periodically.
• Direct Current (DC): Flows only in one direction.

Domestic Electric Circuits

In homes, we receive AC supply of 220V with a frequency of 50 Hz. The system consists of:

• Live wire (Red): Carries current to appliances.
• Neutral wire (Black): Completes the circuit.
• Earth wire (Green): Provides safety by preventing electric shock.

Short Circuiting

Occurs when live and neutral wires touch, causing very low resistance and a large current flow, which can damage appliances.

Overloading

Happens when too many appliances are connected or when supply voltage rises suddenly, leading to excessive current in wires.