Lecture_10

Lecture_10 - Lecture 10 1/18 Electric Current dq dt Current...

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Lecture 10 1/18 Electric Current Current is charges in motion rate at which net positive charges move through a cross sectional area dt dq t Q I units of current is ampere (A) 1 A = 1 C/s Current is a scalar, signed quantity, whose sign corresponds to the direction of motion of net positive charges by convention A A d J I J is current density , a vector with units (A/m 2 )
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Lecture 10 2/18 Ohm’s Law Resistance Resistance in terms of Resistivity Power dissipation I V R V R I A L R constant R Ohm’s Law R V R I V I dt dU P 2 2
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Lecture 10 3/18 EMF Electromotive Force An EMF device is a charge pump that can maintain a potential difference across two terminals by doing work on the charges when necessary (Volts) ] [ V Emf dq dW Emf Examples: battery, fuel cell, electric generator, solar cell, fuel cell, thermopile, … Converts energy (chemical, mechanical, solar, thermal, …) into electrical energy. Within the EMF device, positive charges are lifted from lower to higher potential. If work dW is required to lift charge dq ,
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Lecture 10 4/18 Resistors in Parallel Resistors connected on separate branches by a wire that splits and then reconnects are connected in parallel Potential (V) is the same across resistors in parallel 3 3 2 2 1 1 R I R I R I V Resistors connected similarly can be replaced by equivalent resistance 3 2 1 1 1 1 1 R R R R eq R I I I V ) ( 3 2 1 V V same as
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Lecture 10 5/18 Resistors in Series Resistors connected in a line with no junctions are connected in series Current (I) is the same through all devices in series 0 2 1 R I R I V 3 2 1 R R R R eq R 1 R 2 I I V R eq I V 0 R I V 2 1 R R R same as since
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Lecture_10 - Lecture 10 1/18 Electric Current dq dt Current...

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