Forces on Current-Carrying Wires

  • Moving charges in magnetic fields experience forces.

  • Current in a wire is just a flow of charges.

  • If charges are moving perpendicular to magnetic fields, they experience a force which is applied to the wire.

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    Positive charge moving through stationary wire in magnetic field. This relationship arises from the basic magnetic force: F = qvB sin 0 which for a charge q traveling length L in a wire can be written current I F = ILB sin O or F = ILB ifO=90 F = sin 0 F —— LB sin 0 F = ILB sin O

Example 1: Current Through a Wire

1=100 А\! Э В-Ш Tesla

  • A straight wire of length 1 m carries a current of 100 A through a magnetic field of 1 Tesla. Find the force on the wire

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Electric Motors

Coil rotates clockwise Force Split-ring commutato Force Metal or graphite brush contact

Example 2: Net Torque

  • Determine the direction of the net torque on the current-carrying closed circuit

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Example 3: Force on a Curved Wire

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  • The curved wire carries constant current I through a uniform magnetic field B as shown. Find the net force acting on the wire.

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