Faraday's vs Ampere's Laws and current density

In summary, Faraday's Law states that a time-varying magnetic field can induce an electromotive force (EMF) which in turn can produce an electric current density in a media. This current density is determined by the electric field (E) and the resistivity of the media. Additionally, the equation for EMF and resistance can be substituted for Del X E in the equation -jwB. In a separate discussion, it was found that increasing the feeding frequency and decreasing the number of turns in a solenoid can result in a higher induced EMF.
  • #1
VictorVictor5
13
0
Greetings all,

I know that Faraday's and Ampere's law are related by M.E., but can I say the following?

By Faraday’s Law, a time varying magnetic field induces an electromotive force, which produces an electric current density in a media.

Up until EMF, that's Faraday's, but is the rest of the sentence true? I would assume yes since J=sigma*E, or E=J/sigma to keep it in line with using Del X E = -jwB, or Del X J/sigma=-jwB.

Just trying to confirm.

Thanks!
VV5
 
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  • #2
The EMF can produce a current if there is a circuit. The current will depend on EMF and resistance. The current density will depend on E and resistivity.
 
  • #3
On the right side of Del X E you would have the negative of the time derivative of B. The substitution for E looks fine.
 
  • #4
Thanks to both!
 
  • #5
hi
i have a coil of three turns and the spacing between the turns is 5 mm. i feed the coil with a signal of 13.24 MHz. and i put a solenoid of 3 mm radius 21 cm away from the coil to induce an emf. the solenoid has 23 number of tuns, 28 mm length. the induced emf is 280 mm V (rms) which is almost 10 times more than what i calculated. when i diconnect the coil from the signal generator, the induced voltage is 128 mmV(rms). the net emf= 152 mmVrms..
when the feeding freequency increased to 13.56 MHz and the solenoids number of turns decreased to 22. induced emf =460 mmV (rms) discennected 213 mmV. net induced emf=247 mV (rms).
can any recomand me any think.
thank you
 

FAQ: Faraday's vs Ampere's Laws and current density

1. What is Faraday's Law and how does it relate to current density?

Faraday's Law, also known as the law of electromagnetic induction, states that a changing magnetic field will induce an electric current in a conductor. This is directly related to current density, as the induced current will flow through the conductor and can be measured by the current density, which is the amount of current per unit area.

2. What is Ampere's Law and how is it different from Faraday's Law?

Ampere's Law states that the magnetic field created by a current-carrying conductor is directly proportional to the current and inversely proportional to the distance from the conductor. This law is different from Faraday's Law in that it describes the relationship between a current and a magnetic field, while Faraday's Law describes the relationship between a changing magnetic field and an induced current.

3. How do Faraday's and Ampere's Laws play a role in electromagnetic waves?

Faraday's and Ampere's Laws are fundamental principles in electromagnetism, and they play a crucial role in understanding the behavior of electromagnetic waves. According to Faraday's Law, a changing magnetic field can induce an electric current, which is the basis for how electromagnetic waves are generated. Ampere's Law also helps in understanding the behavior of electromagnetic waves by describing the relationship between a current and a magnetic field.

4. How is current density calculated and why is it important?

Current density is calculated by dividing the current flowing through a conductor by the cross-sectional area of the conductor. It is an important concept in electromagnetism as it helps in understanding and analyzing the flow of electric current through a material. It can also be used to determine the strength of a magnetic field and the amount of power dissipated in a conductor.

5. How do Faraday's and Ampere's Laws apply to practical applications in everyday life?

Faraday's and Ampere's Laws have numerous practical applications in everyday life. For example, electromagnetic induction is used in generators to produce electricity, and Ampere's Law is used in devices such as electric motors and transformers. These laws also play a crucial role in the development of technologies such as wireless charging, electromagnets, and magnetic levitation systems.

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