Electrical Circuit Laws : Ohm’s , Faraday’s, Lenz’s, Fleming’s ,Kirchhoff’s Law
Electric Laws and theorems:
Ohm’s law:
Ohm’s law states that the current I flowing in a circuit is directly proportional to the applied voltage V and inversely proportional to the resistance R, as long as the temperature remains constant.
Laws of electromagnetic induction:
Faraday’s laws of Electromagnetic induction:
Faraday’s Laws of Electromagnetic Induction are fundamental principles in electromagnetism, discovered by the British scientist Michael Faraday. They describe how a changing magnetic field can produce an electromotive force (EMF) in a conductor.
Faraday’s First Law states that whenever the magnetic flux through a circuit changes, an EMF is induced in the circuit. This induced EMF causes a current to flow if the circuit is closed.
Faraday’s Second Law quantifies the induced EMF. It states that the magnitude of the induced EMF is directly proportional to the rate of change of magnetic flux linkage.
Together, these laws form the foundation for understanding how electric generators, transformers, inductors, and many other electromagnetic devices work. They highlight the relationship between electricity and magnetism and have numerous practical applications in modern technology.
Lenz’s Law: (Direction of induced electromagnetic fields)
Lenz’s Law is a fundamental principle in electromagnetism, named after the physicist Heinrich Lenz. It states that the direction of the induced electromotive force (EMF) and hence the induced current in a closed loop is such that it opposes the change in magnetic flux that produced it. This law is a manifestation of the conservation of energy and Newton’s third law of motion.
When a changing magnetic field induces a current in a conductor, the generated current creates its own magnetic field. According to Lenz’s Law, this induced magnetic field will always oppose the initial change in magnetic flux. For example, if the magnetic flux through a loop increases, the induced current will flow in a direction that creates a magnetic field opposing this increase. Conversely, if the magnetic flux decreases, the induced current will flow in a direction that supports the magnetic field, attempting to maintain the flux.
Fleming’s right hand rule:
Let the thumb, index and middle fingers of your right hand be extended so that they are all perpendicular to each other. If the first finger points in the direction of the magnetic field, the thumb points in the direction of the conductor’s motion with respect to the magnetic field, then the second finger points in the direction of the induced emf.
The direction of force exerted on a conductor can be predetermined using Fleming’s left-hand rule (often called the motor rule).
Fleming’s left hand rule:
Let the thumb, index and middle fingers of the left hand be extended so that they form right angles to each other. If the first finger points in the direction of the magnetic field, the second finger points in the direction of the current, and then the thumb points in the direction of the movement of the conductor.
Theorems of DC circuit theory:
Kirchhoff’s Laws:(a) Current law:At any junction in an electrical circuit, the total current flowing to that junction is equal to the total current flowing from the junction.
(b) Voltage law:In any closed circuit of a network, the algebraic sum of the voltage drops (i.e., products of current and resistance) taken around the circuit is equal to the e.m.f. resulting or acting in that loop.
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