Circuit Basics

Posted December 30, 2015

by Lensyl Urbano

Studying voltage and current in circuits can start with two laws of conservation.

  • KCL: Current flow into a node must equal the flow out of the node. (A node is a point on the wire connecting components in a circuit–usually a junction).
(KCL: Kirchoff's Current Law) Current flowing into any point on a circuit is equal to the current flowing out of it, A simple circuit with a voltage source (like a battery) and a resistor.

(KCL: Kirchoff’s Current Law) Current flowing into any point on a circuit is equal to the current flowing out of it, A simple circuit with a voltage source (like a battery) and a resistor.

  • KVC: The sum of all the voltage differences in a closed loop is zero.

KVL: The voltage difference across the battery (9 Volts) plus the voltage difference across the resistor (-9 Volts) is equal to zero.

KVL: The voltage difference across the battery (9 Volts) plus the voltage difference across the resistor (-9 Volts) is equal to zero.

Things get more interesting when we get away from simple circuits.

Current flow into a node (10 A) equals the flow out of the node (7 A + 3 A).

Current flow into a node (10 A) equals the flow out of the node (7 A + 3 A).

Note that the convention for drawing diagrams is that the current move from positive (+) to negative (-) terminals in a battery. This is opposite the actual flow of electrons in a typical wired circuit because the current is a measure of the movement of negatively charged electrons, but is used for historical reasons.

Based on the MIT OpenCourseWare Introduction to Electrical Engineering and Computer Science I Circuits 6.01SC Introduction to Electrical Engineering and Computer Science Spring 2011.

Citing this post: Urbano, L., 2015. Circuit Basics, Retrieved May 27th, 2017, from Montessori Muddle: http://MontessoriMuddle.org/ .
Attribution (Curator's Code ): Via: Montessori Muddle; Hat tip: Montessori Muddle.

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