Edexcel iGCSE Physics -6.8–6.10P Magnetic Fields around Current-Carrying Conductors and Field Patterns- Study Notes- New Syllabus

Edexcel iGCSE Physics -6.8–6.10P Magnetic Fields around Current-Carrying Conductors and Field Patterns- Study Notes- New syllabus

Edexcel iGCSE Physics -6.8–6.10P Magnetic Fields around Current-Carrying Conductors and Field Patterns- Study Notes -Edexcel iGCSE Physics – per latest Syllabus.

Key Concepts:

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Edexcel iGCSE Physics -Concise Summary Notes- All Topics

Magnetic Field Around a Current-Carrying Conductor

When an electric current flows through a conductor, it produces a magnetic field around the conductor. This shows a direct link between electricity and magnetism.

Current-Carrying Conductor – Magnetic Effect

Statement: An electric current in a conductor produces a magnetic field around the conductor.

Key idea: The magnetic field exists only while the current is flowing.

Shape of the Magnetic Field

For a straight current-carrying conductor:

  • Magnetic field lines form concentric circles around the wire.
  • The conductor is at the centre of the circles.
  • The field becomes weaker further from the wire.

Direction of the Magnetic Field

The direction of the magnetic field around a straight conductor is found using the right-hand grip rule.

  • Thumb points in the direction of the current.
  • Curled fingers show the direction of the magnetic field.

Key point: Reversing the current reverses the direction of the magnetic field.

Factors Affecting the Magnetic Field Strength

  • Increasing the current increases the magnetic field strength.
  • Magnetic field strength decreases with distance from the conductor.
  • Using a coil increases the strength of the magnetic field.

Evidence for the Magnetic Field

  • A compass needle placed near the wire deflects.
  • The deflection increases when current increases.
  • No deflection occurs when current is switched off.

Example

A straight vertical wire passes through a piece of cardboard. A current flows upward through the wire. Describe the magnetic field pattern produced and explain how its direction can be determined.

▶️ Answer / Explanation
  • The magnetic field forms concentric circles around the wire.
  • The wire is at the centre of the circles.
  • The right-hand grip rule is used.
  • The thumb points upward (direction of current).
  • The curled fingers show the field direction.

Example

A student increases the current in a straight wire while observing a nearby compass. Explain what happens to the compass deflection and why.

▶️ Answer / Explanation
  • Increasing the current increases the magnetic field strength.
  • A stronger magnetic field exerts a larger force on the compass needle.
  • The compass deflects through a greater angle.
  • This confirms that current produces a magnetic field.

Magnetic Field Patterns of Current-Carrying Conductors

When an electric current flows, it produces a magnetic field. The shape of the magnetic field depends on the shape of the conductor. You must be able to draw and interpret the magnetic field patterns for different current-carrying conductors.

Magnetic Field Around a Straight Wire

Pattern:

  • Magnetic field lines form concentric circles around the wire.
  • The wire is at the centre of the circles.
  • Field strength decreases with distance from the wire.

Direction:

  • Use the right-hand grip rule.
  • Thumb points in direction of current.
  • Curled fingers show field direction.

Magnetic Field Around a Flat Circular Coil

Pattern:

  • Field lines form circles around each part of the wire.
  • Inside the coil, field lines combine to form a stronger field.
  • The field is strongest at the centre of the coil.

Direction:

  • Use the right-hand rule.
  • Fingers follow current direction around the coil.
  • Thumb points in direction of the magnetic field through the centre.

Magnetic Field Around a Solenoid

Pattern:

  • Magnetic field is similar to that of a bar magnet.
  • Inside the solenoid, field lines are straight, parallel, and evenly spaced.
  • This shows a strong, uniform magnetic field inside.

Polarity:

  • One end acts as a north pole.
  • The other end acts as a south pole.
  • Reversing the current reverses the poles.

Comparing the Three Field Patterns

  • Straight wire → circular field lines.
  • Circular coil → concentrated field at centre.
  • Solenoid → strong, uniform internal field.

Key idea: The solenoid produces the most useful magnetic field for applications such as electromagnets.

Example

A student draws magnetic field lines around a solenoid and notices that the lines inside the solenoid are straight and evenly spaced. Explain what this shows about the magnetic field inside the solenoid.

▶️ Answer / Explanation
  • Straight lines show the field has a constant direction.
  • Even spacing shows constant field strength.
  • This indicates a uniform magnetic field.
  • The field inside the solenoid is strong.

Example

A current flows anticlockwise in a flat circular coil when viewed from above. State the direction of the magnetic field at the centre of the coil and explain your answer.

▶️ Answer / Explanation
  • Use the right-hand rule.
  • Fingers curl in the direction of the current.
  • The thumb points upward.
  • The magnetic field at the centre is upwards.
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