Basic Law related to Electrical Engineering

The topic contains some electrical basic law and terminology Ohm's Law, KVL & KCL, Voltage and Current Division Rule, Faraday Laws of electromagnetic Induction and Lenz Law

1. BASIC LAWS USED IN ELECTRICAL ENGINEERING

2. CONTENT Ohm’s Law Kirchhoff Current Law Kirchhoff's Voltage Law Voltage and Current Division Rule Lenz Law Screw Law Faraday Law of Electromagnetic Induction

3. Ohm’s Law Georg Simon Ohm (1789 – 1854) German professor who publishes a book in 1827 that includes what is now known as Ohm's law. Ohm's Law: The voltage across a resistor is directly proportional to the current flowing through it . According to ohms law V∞ I where R is constant where, V = Voltage in Volts I = Current in Amperes R= Resistance in Ohms

4. Terminology Definition Voltage: A force that pushes the current through the circuit (in this picture it would be equivalent to gravity ). Current: The actual “substance” that is flowing through the wires of the circuit (electrons !). Resistance: Friction that impedes flow of current through the circuit (rocks in the river )

5. Gustav Robert Kirchhoff (1824 – 1887 ) “Kirchhoff Law” Born in Prussia (now Russia), Kirchhoff developed his "laws" while a student in 1845. These laws allowed him to calculate the voltages and currents in multiple loop circuits.

6. Kirchhoff Current Law KCL The algebraic sum of the currents entering a node is zero or At any node the incoming current is equal to outgoing current.

7. Kirchhoff Voltage Law KVL In any closed path (or circuit) in a network, the algebraic sum of the IR product is equal to the EMF in that path . In other words, in any closed loop (which also known as Mesh), the algebraic sum of the EMF applied is equal to the algebraic sum of the voltage drops in the elements. Kirchhoff’s second law is also known as Voltage Law or Mesh law . Counter-clockwise: Clockwise:

8. Voltage Division Rule 8

9. Current Division Rule Current divides in inverse proportion to the resistances

10. 10 Source Exchange We can always replace a voltage source in series with a resistor by a current source in parallel with the same resistor and vice-versa. Doing this, however, makes it impossible to directly find the original source current.

11. Lenz Law Lenz's law  is named after the German scientist H. F. E. Lenz in 1834.  Lenz's law  obeys Newton's third law of motion ( i.e to every action there is always an equal and opposite reaction) and the conservation of energy ( i.e energy may neither be created nor destroyed and therefore the sum of all the energies in the system is a constant ).

12. Statement: Lenz's law states that when an emf is generated by a change in  magnetic flux  according to Faraday's Law, the polarity of the induced emf is such, that it produces an  current  that's  magnetic field  opposes the change which produces it . w here , ε = induced emf δΦ B  = change in  magnetic flux N = No of turn of coil

13. Right hand Rule or Screw Rule The right hand  screw rule  can be used when a direction must be determined based upon a rotational direction, or vice versa.

14. Faraday 1 st Laws of “Electromagnetic induction” Whenever a conductor is placed in a varying magnetic field an EMF gets induced across the conductor (called as induced emf), and if the conductor is a closed circuit then induced current flows through it. Magnetic field can be varied by various methods - 1. By moving magnet 2. By moving the coil 3. By rotating the coil relative to magnetic field.   E = N (d Φ/ dt )    (volts)

15. Faraday 2 nd Laws of “Electromagnetic induction” The magnitude of induced emf is equal to the rate of change of flux linkages with the coil. The flux linkages is the product of  number of turns  and  the flux associated with the coil.

16. Any Query…??? Thank You