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11.1 Electric Current

Syllabus
2024
Topic
11.1
Level
—

Learning objectives

11.1A—Describe the movement of electric charges through a mediumDescribe the movement of electric charges through a medium.• Current is the rate at which charge passes through a cross-sectional area of a wire. Relevant equation: =Idq dt- i. Current within a conductor consists of charge carriers traveling through the conductor with an average drift velocity. Relevant equation: =In qv Ad- ii. Electric charge moves in a circuit in response to an electric potential difference, sometimes referred to as electromotive force, or emf ( ).- iii. If the current is zero in a section of wire, the net motion of charge carriers in the wire is also zero, although individual charge carriers will not have zero speed.• Current density is the flow of charge per unit area. Relevant equation:- i. Current density is related to the motion of the charge carriers within a conductor. Relevant equation: =Jn qvd- ii. Current density is a vector quantity.- iii. A potential difference across a conductor creates an electric field within the conductor that is proportional to the resistivity of the conductor and the current density. Relevant equation:• If a function of current density is given, the total current can be determined by integrating the current density over the area. Derived equation:• Although current is a scalar quantity, it does have a direction. Because its direction is relative to the current carrier and not space, current does not obey the laws of vector addition and has no vector components.- i. The direction of conventional current is chosen to be the direction in which positive charge would move.- ii. In common circuits, the current is actually due to the movement of electrons (negative charge carriers).

11.1.A—Describe the movement of electric charges through a medium

Describe the movement of electric charges through a medium.

  • Current is the rate at which charge passes through a cross-sectional area of a wire. Relevant equation: =Idq dt
    • i. Current within a conductor consists of charge carriers traveling through the conductor with an average drift velocity. Relevant equation: =In qv Ad
    • ii. Electric charge moves in a circuit in response to an electric potential difference, sometimes referred to as electromotive force, or emf ( ).
    • iii. If the current is zero in a section of wire, the net motion of charge carriers in the wire is also zero, although individual charge carriers will not have zero speed.
  • Current density is the flow of charge per unit area. Relevant equation:
    • i. Current density is related to the motion of the charge carriers within a conductor. Relevant equation: =Jn qvd
    • ii. Current density is a vector quantity.
    • iii. A potential difference across a conductor creates an electric field within the conductor that is proportional to the resistivity of the conductor and the current density. Relevant equation:
  • If a function of current density is given, the total current can be determined by integrating the current density over the area. Derived equation:
  • Although current is a scalar quantity, it does have a direction. Because its direction is relative to the current carrier and not space, current does not obey the laws of vector addition and has no vector components.
    • i. The direction of conventional current is chosen to be the direction in which positive charge would move.
    • ii. In common circuits, the current is actually due to the movement of electrons (negative charge carriers).