OhmsLaw

OhmsLaw - Electric Current Electric field exerts forces on...

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1 Electric Current Electric field exerts forces on charges inside it; Charges move under the influence of an electric field. The amount of charge moves through a cross section in unit time is defined as the electric current. For an electric field in vacuum, the moving charge can be either positive (ions) or negative (electrons). In a CRT tube (any of you still have those bulky old TV set?), the moving charge inside the CRT tube (vacuum) is electron. Often the electric field is “guided” by a conductor wire. What is flowing in the wire are the electrons, and they form the current. E V V V V dt dq I

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Electric Current The direction of the current is defined as the direction of the moving positive charge, or, the direction of the electric field which always points from high potential to low potential. The unit of the electric current is Ampere in the SI system. The ampere (Amp. or A) is an SI base unit. Other SI base units are meter, kilogram (for mass), second, kelvin (for temperature), mole (quantity of matter) and candela (luminous intensity). The definition of ampere: The ampere is that constant current which, if maintained in two straight parallel conductors of infinite length, of negligible circular cross-section, and placed 1 meter apart in vacuum, would produce between these conductors a force equal to 2·10 –7 Newton per meter of length.
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This note was uploaded on 05/06/2008 for the course PHYS 1304 taught by Professor Ye during the Spring '08 term at SMU.

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OhmsLaw - Electric Current Electric field exerts forces on...

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