FIELD AROUND CURRENT-CARRYING CONDUCTORS

• A magnetic field exists around any wire that is conducting an electric current.

Investigations:

1. Magnetic field of a straight wire
2. Magnetic field pattern of a circular loop
3. Magnetic field pattern of a solenoid

STRAIGHT WIRE MAGNETIC FIELD

Aim: To map the magnetic field around a current-carrying conductor.

1. Set up a circuit with a straight wire.
2. Switch on the circuit and softly tap the cardboard on which iron filings have been sprinkled.
   • Observation: The filings settle in concentric circles around the wire, becoming less concentrated as the distance from the center increases.

Discussion:

• The magnetic field forms concentric circles around the conductor.
• The field strength decreases with distance from the wire.
• The direction of the magnetic field is determined by the current direction and lies in a plane perpendicular to the wire.

Illustration required

CIRCULAR LOOP

Aim: To demonstrate the magnetic field of a loop carrying current.

1. Pass a wire through two holes in a cardboard and connect it to a DC supply.
2. Sprinkle iron filings on the cardboard and observe the pattern.

Observation:

• The iron filings arrange themselves in a pattern around the loop.
• The right-hand grip rule applies: if the fingers of the right hand encircle the current loop in the direction of the current, the thumb points in the direction of the magnetic field.

Illustration required

FLEMING’S RIGHT-HAND RULE

• Thumb points to the direction of motion, the first finger points to the magnetic field, and the second finger points to the current direction.

Illustration required

MAGNETIC FIELD PATTERN OF A SOLENOID

• A solenoid is formed by many loops of wire, and its magnetic field is much stronger than that of a single loop.

Aim: To demonstrate the magnetic field of a solenoid.

1. Create a solenoid by winding many loops of wire around a cardboard.
2. Sprinkle iron filings on the card and connect the solenoid to a DC power source.

Observation: The filings arrange themselves along the magnetic field lines.

• The magnetic field inside a solenoid is proportional to the current and the number of turns per unit length, and it remains constant inside the solenoid.

Illustration required

FORCE ON A CURRENT-CARRYING CONDUCTOR IN A MAGNETIC FIELD

• A strip of aluminum placed in a magnetic field experiences no force, but when current is passed through it, the strip moves upwards.

Discussion:

• The magnetic force on the current-carrying wire is perpendicular to both the magnetic field and the direction of current.
• The force is maximal when the wire is perpendicular to the magnetic field.

FLEMING’S LEFT-HAND RULE

• Used to determine the direction of the force on a current-carrying conductor in a magnetic field.
  • Thumb points to the force, first finger points to the field, and second finger points to the current.

Illustration required