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Current entering the node is positive and leaving the node is negative

Kirchhoff's Current Law ( KCL):. The algebraic sum of all the currents at any node in a circuit equals zero. Current entering the node is positive and leaving the node is negative. Current entering the node is negative and leaving the node is positive.

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Current entering the node is positive and leaving the node is negative

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  1. Kirchhoff's Current Law ( KCL): The algebraic sum of all the currents at any node in a circuit equals zero. Current entering the node is positive and leaving the node is negative Current entering the node is negative and leaving the node is positive Note the algebraic sign is regardless if the sign on the value of the current

  2. Figure 1.14 Illustration of Kirchhoff’s current law (KCL).

  3. KCL also applies to larger and closed regions of circuit called supernodes

  4. Example 1.3: Determine the currents ix, iy and iz KCL at node d ix+3=2 ix = 2-3 = -1A KCL at node a ix+ iy +4 = 0 iy = -3A KCL at node b 4 + iz + 2 = 0 iz = -6A We could have applied KCL at the supernode to get iy + 4A + 2A = 3A Thus iy = -3

  5. Figure 1.17Example 1.4.

  6. Kirchhoff Voltage Law (KVL) The algebraic sum of all the voltages around any closed path in a circuit equals zero. First we have to define a closed path A closed path or a loop is defined as starting at an arbitrary node, we trace closed path in a circuit through selected basic circuit elements including open circuit and return to the original node without passing through any intermediate node more than once abea bceb cdec aefa abcdefa

  7. Kirchhoff Voltage Law (KVL) The algebraic sum of all the voltages around any closed path in a circuit equals zero. The "algebraic" correspond to the reference direction to each voltage in the loop. Assigning a positive sign to a voltage rise ( - to + ) Assigning a negative sign to a voltage drop ( + to - ) OR Assigning a positive sign to a voltage drop ( + to - ) Assigning a negative sign to a voltage rise ( - to + )

  8. Example We apply KVL as follows: Loop 1 Loop 2

  9. Figure 1.23 Another example of the application of KVL.

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