Basic Electrical Engineering (ES103) Lecture Notes PDF

BASIC ELECTRICAL ENGINEERING (ES103) KAMLESH PANDEY ASSISTANT PROFESSOR DEPARTMENT OF ELECTRICAL AND ELECTRONICS ENGINEERING AMITY SCHOOL OF ENGINEERING AND TECHNOLOGY, AUUP  MODULE 1 DC CIRCUITS AND NETWORK THEOREMS LECTURE 4 ...

BASIC ELECTRICAL ENGINEERING (ES103) KAMLESH PANDEY ASSISTANT PROFESSOR DEPARTMENT OF ELECTRICAL AND ELECTRONICS ENGINEERING AMITY SCHOOL OF ENGINEERING AND TECHNOLOGY, AUUP  MODULE 1 DC CIRCUITS AND NETWORK THEOREMS LECTURE 4  KIRCHHOFF’S CURRENT LAW (KCL) KCL states that, “the algebraic sum of the currents meeting at a junction in an electrical circuit is zero” An algebraic sum is one in which the sign of the quantity is taken into account. For example, consider four conductors carrying currents I , I , I and I and meeting at point O as shown in Fig.  KIRCHHOFF’S CURRENT LAW (KCL) If we take the signs of currents flowing towards point O as positive, then currents flowing away from point O will be assigned negative sign. Thus, applying Kirchhoff’s current law to the junction O in Fig., we have, (I ) + (-I ) + (-I ) + (I ) = 0 or, I +I = I +I i.e. Sum of incoming currents = Sum of outgoing currents The sum of currents flowing towards any junction in an electrical circuit is equal to the sum of currents flowing away from that junction. Kirchhoff’s current law is also called junction rule.  KIRCHHOFF’S VOLTAGE LAW (KVL) KVL states that, “In any closed electrical circuit or mesh, the algebraic sum of all the electromotive forces (e.m.fs) and voltage drops in resistors is equal to zero” Algebraic sum of e.m.fs + Algebraic sum of voltage drops = 0 The validity of Kirchhoff’s voltage law can be easily established by referring to the closed loop ABCDA shown in Fig. If we start from any point (say point A) in this closed circuit and go back to this point (i.e., point A) after going around the circuit, then there is no increase or decrease in potential.  KIRCHHOFF’S VOLTAGE LAW (KVL) This means that algebraic sum of the e.m.fs of all the sources (here only one e.m.f. source is considered) met on the way plus the algebraic sum of the voltage drops in the resistances must be zero. Kirchhoff’s voltage law is based on the law of conservation of energy, i.e., net change in the energy of a charge after completing the closed path is zero.  Maxwell’s Mesh Current Method In this method, Kirchhoff’s voltage law is applied to a network to write mesh equations in terms of mesh currents instead of branch currents. Steps to solve circuit using Maxwell’s Mesh Current Method – 1. Each mesh is assigned a separate mesh Mesh ABDA. current. 2. This mesh current is assumed to flow clockwise around the perimeter of the mesh without splitting at a junction into branch currents. 3. Kirchhoff’s voltage law is then applied to Mesh BCDB. write equations in terms of unknown mesh currents. 4. The branch currents are then found by taking the algebraic sum of the mesh currents which are common to that branch  Numerical In the network shown in Fig. find the magnitude and direction of each branch current by mesh current method Solution  Numerical In the network shown in Fig. find the magnitude and direction of each branch current by mesh current method Solution  PRACTICE PROBLEM 1. Determine the current supplied by each battery in the circuit shown in Fig 2. Determine the current in the 8 ohmbranch in the circuit shown in Fig  PRACTICE PROBLEM 1. Determine the current supplied by each battery in the circuit shown in Fig SOLUTION  PRACTICE PROBLEM Determine the current in the 8 ohmbranch in the circuit shown in Fig SOLUTION