
Faraday's law of electromagnetic induction states that electromagnetic force (EMF) is induced when there is a change in magnetic flux over time. The law describes the relationship between a changing magnetic field and the electric circuit. The magnetic flux through a wire loop is proportional to the number of magnetic field lines passing through the loop. When the flux changes due to variations in the magnetic field or the movement or deformation of the wire loop, the wire loop acquires an EMF, which is the energy available from a unit charge that has travelled once around the wire loop.
| Characteristics | Values |
|---|---|
| Faraday's Law | The electromotive force around a closed path is equal to the negative of the time rate of change of the magnetic flux enclosed by the path |
| Faraday's Second Law | The induced electromotive force (emf) in a coil is equal to the rate of change of flux linkage |
| Flux Linkage | The product of the number of turns in the coil and the flux associated with the coil |
| Relationship with Electromagnetic Induction | Faraday's Law states that emf appears on a conductive loop when the magnetic flux through the surface enclosed by the loop varies in time |
| Direction of Induced Current | Embedded in Faraday's Law is the direction of the induced current in the loop |
| Relationship with Electric and Magnetic Fields | The Maxwell-Faraday equation describes the fact that a spatially varying electric field accompanies a time-varying magnetic field |
| Calculation of Magnetic Flux | Generally, the calculation is simple as one mostly considers flat loops, but it becomes more complex when considering the differential form of Faraday's Law |
| Right-Hand Rule | A way to remember the sign convention; if your thumb points in the direction of magnetic flux increase, the current flows in the opposite direction to the curl of the fingers |
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What You'll Learn

Faraday's Law of Induction
Faraday's law can be summarized as follows: when a magnetic field interacting with an electric circuit changes, it induces a voltage or electromotive force (EMF) in the circuit. This phenomenon is known as electromagnetic induction. In other words, Faraday's law states that a changing magnetic field and a changing electric field are intimately linked.
Faraday's law consists of two parts: the first law describes the induction of EMF in a conductor, while the second law quantifies the EMF produced. According to the first law, when a conductor is placed in a varying magnetic field, an EMF is induced. If the conductor circuit is closed, this results in an induced current. The second law states that the induced EMF in a coil is equal to the rate of change of flux linkage, which is the product of the number of turns in the coil and the magnetic flux associated with the coil.
Faraday's law can be expressed mathematically as EMF = −dΦ/dt, where EMF is the electromotive force and dΦ/dt represents the rate of change of magnetic flux over time. This equation demonstrates that the magnitude of the induced EMF is directly proportional to the rate of change of magnetic flux.
Faraday's law has important practical applications. For example, electrical equipment like transformers and induction cookers operate based on the principles of Faraday's law. Additionally, musical instruments like electric guitars and violins also utilize Faraday's law.
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The Relationship Between Electric Circuits and Magnetic Fields
Electricity and magnetism are interconnected phenomena associated with the electromagnetic force. Together, they form the basis for electromagnetism. A moving electric charge always generates a magnetic field, and a magnetic field can induce the movement of electric charge, producing an electric current.
Every moving electric charge has a magnetic field. For example, the orbiting electrons of atoms produce a magnetic field, there is a magnetic field associated with power lines, and hard discs and speakers rely on magnetic fields to function.
A magnetic field can be induced by moving a loop of wire toward or away from a magnetic field, inducing a current in the wire. The direction of the current depends on the direction of the movement.
Faraday's second law of electromagnetic induction states that the induced electromotive force (emf) in a coil is equal to the rate of change of flux linkage. The flux linkage is the product of the number of turns in the coil and the flux associated with the coil.
A transformer consists of two separate coils (or more) placed on either side of an iron core. The alternating voltage in the primary circuit creates a changing current, which induces magnetic flux in the iron core. This magnetic field induces a voltage in the secondary coil.
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The Maxwell-Faraday Equation
The equation describes the relationship between a time-varying magnetic field and a spatially varying electric field. In other words, it explains that a changing magnetic field will always be accompanied by a changing electric field and vice versa. This is expressed mathematically as:
> ∇ × E = −∂tB
Where:
- ∇ × is the curl operator
- E(r, t) is the electric field
- B(r, t) is the magnetic field
- R represents the position
- T represents time
The significance of the Maxwell-Faraday equation lies in its ability to mathematically describe the relationship between electric and magnetic fields, providing a foundation for understanding electromagnetic radiation and its propagation through space. This equation, along with the other Maxwell's equations, has inspired the development of relativity theory and has applications in quantum mechanics.
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The Magnetic Flux Through a Wire Loop
Faraday's laws of electromagnetic induction describe the relationship between an electric circuit and a magnetic field. Faraday's first law states that an electromotive force (emf) is induced when the magnetic flux across a coil changes with time. The magnetic flux through a wire loop can be changed in several ways.
Firstly, increasing the magnetic field through the wire loop will change the magnetic flux. This can be achieved by moving a magnet towards or away from the coil, thereby altering the magnetic field strength within the loop.
Secondly, increasing the area of the wire loop will also change the magnetic flux. This is because the magnetic flux is dependent on the number of magnetic field lines passing through the loop. By increasing the loop's area, more field lines can pass through, resulting in a change in magnetic flux.
Additionally, the magnetic flux is related to the number of turns in the coil. The flux linkage, as defined by Faraday's law, is the product of the number of turns in the coil and the magnetic flux associated with the coil. Therefore, by changing the number of turns in the coil, the magnetic flux through the wire loop will be affected.
It is important to note that the magnetic flux is independent of the shape of the wire loop. This means that the magnetic flux remains constant even if the loop is deformed while keeping the other factors, such as the magnetic field and the number of turns, constant.
In summary, the magnetic flux through a wire loop can be altered by changing the magnetic field strength, the area of the loop, or the number of turns in the coil. These principles form the basis of electromagnetic induction and have been extensively studied by scientists such as Faraday, Henry, and Heinrich Friedrich Lenz, who contributed to our understanding of the relationship between electric circuits and magnetic fields.
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The Direction of the Induced Current
Faraday's law of electromagnetic induction, also known as Faraday's law, is a basic law of electromagnetism that helps us understand how a magnetic field interacts with an electric circuit to produce an electromotive force (EMF). This phenomenon is known as electromagnetic induction.
Faraday's law states that a change in magnetic flux over time induces an EMF, which in turn induces a current in a closed circuit. The direction of the induced current is crucial and is given by the negative sign in Faraday's law, which is also known as Lenz's law.
Lenz's law, formulated by Heinrich Lenz, states that the induced current will flow in a direction that opposes the change in magnetic flux. In other words, the induced current creates a magnetic field that counteracts the change in the original magnetic field. This is often referred to as the conservation of energy.
Faraday's experiments demonstrated that when a magnetic field changes, it induces an EMF, and subsequently, a current in a closed circuit. The direction of this induced current can be determined by the left-hand rule, where the curved fingers of the left hand are aligned with the loop, and the stretched thumb indicates the direction of the normal to the area enclosed by the loop.
Additionally, the right-hand rule is also used to determine the direction of the induced current. According to this rule, if the area enclosed by the circuit increases, the induced field must be in the opposite direction of the existing field. This ensures that the induced current opposes the change in flux, as dictated by Lenz's law.
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Frequently asked questions
Faraday's Law of electromagnetic induction states that the electromotive force around a closed path is equal to the negative of the time rate of change of the magnetic flux enclosed by the path.
Magnetic flux is a fundamental part of Faraday's Law. The law states that when the magnetic flux through the surface enclosed by a conductive loop varies in time, an induced electromotive force (emf) appears on the loop.
The formula for Faraday's Law is:
ε = electromotive force
Φ = magnetic flux
N = the number of turns in the coil











































