Electric currents produce magnetic fields - Magnetism

Electric currents produce magnetic fields

Lessons

Notes:

In this lesson, we will learn:

  • An electric current produces a magnetic field
  • Magnetic force on a current-carrying wire placed in a magnetic field

Notes:

An electric current produces a magnetic field
  • A compass needle placed near a straight section of current-carrying wire experience a force, causing the needle to align tangent to a circle around the wire.
  • Magnetic field lines produced by a current-carrying wire are in the form of circles with the wire at their center.
  • Using right-hand rule, we can find the direction of the magnetic field produced by a current-carrying wire.
  • Right-hand rule: grasp the wire with your right hand, so your thumb points in the direction of the conventional ( positive) current; then your fingers will encircle the wire in the direction of the magnetic field.

  • Electric Currents Produce Magnetic Fields

Magnetic force on a current-carrying wire placed in a magnetic field

  • A straight wire is placed in the magnetic field between the poles of a magnet when a current flows in the wire, a magnetic force will be exerted on the wire.
  • The direction of the force is always perpendicular to the direction of the current and also perpendicular to the direction of the magnetic field.
  • Using right-hand rule we can find the direction of the magnetic force.
  • Right-hand rules:
    1. Thumb points to the direction of the current,
    2. Fingers point to the direction of the magnetic field
    3. Palm points towards the direction of the electromagnetic force.

    Electric Currents Produce Magnetic Fields

  • The magnitude of the electromagnetic force (in Newton) is calculated using the following equation:


  • F=IIBsinθF = IIB \sin \theta

    I \qquad I = current in the wire, in ampere (A)
    B \qquad B = magnetic field, in tesla (T)
    θ \qquad \theta = the angle between the current direction and the magnetic field. 

Note:
  • When current is perpendicular to the filed lines, θ \theta = 90°, the force is the strongest,
    Fmax=IIBF_{max} = IIB
  • When the wire is parallel to the magnetic field lines, θ \theta = 0°, there is no force at all.
  • Intro Lesson
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Electric currents produce magnetic fields

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