Faraday's and Lenz's law application

• cseil
In summary, the conversation discusses a rectangular coil rotating around an axis with angular velocity, in a magnetic field. When the coil is perpendicular to the axis, the flux of B is 0. The procedure for calculating the emf and its maximum value is correct. The reason for the maximum emf occurring when the flux is 0 is because what matters is the rate of change of the flux, not its actual value.

Homework Statement

A rectangular coil with a and b sides can rotate around the axis AA' with angular velocity ω. It is in a magnetic field as in figure.

Calculate the flux of B when the coil is orthogonal to the axis AA'. Calculate the $\epsilon_{max}$ and express the position of the coil.

Homework Equations

$\epsilon = -\frac{d}{dt} \phi_B$

The Attempt at a Solution

The flux when the coil is orthogonal to the axis AA' is 0.

$\phi_B = NBabcos\theta$

$\theta$ is 90°, so the flux is 0.

Now I calculate the emf.
$\epsilon = -\frac{d}{dt} \phi_B = NBab\omega sin(\omega t)$

The emf is max when $sin(\theta)$ is 1, so when $\theta$ is 90°.

Is it correct my procedure?
If yes, why emf is maximum when flux is 0?

cseil said:
Calculate the flux of B when the coil is orthogonal to the axis AA'.
Since the coil rotates about that axis, it is always orthogonal to it. I assume you mean when the plane of the coil is perpendicular to the surface of the drawing.

cseil said:
Is it correct my procedure?
Yes.

cseil said:
If yes, why emf is maximum when flux is 0?
What matters is not where the emf is maximum but where its rate of change is maximum.

Edit: Oops... I meant flux, not emf, of course.

Last edited:
Doc Al said:
Since the coil rotates about that axis, it is always orthogonal to it. I assume you mean when the plane of the coil is perpendicular to the surface of the drawing.

Yes, sorry, I meant that.
Thank you!

1. What is Faraday's law and how is it applied?

Faraday's law states that a changing magnetic field will induce an electric current in a conductor. This principle is commonly applied in generators and transformers to convert mechanical energy into electrical energy.

2. What is Lenz's law and why is it important?

Lenz's law is an extension of Faraday's law and states that the direction of the induced current will oppose the change in magnetic flux that caused it. This law is important because it helps us understand the behavior of electromagnetic systems and allows us to predict the direction of induced currents.

3. How are Faraday's and Lenz's laws used in everyday devices?

Faraday's and Lenz's laws are used in many everyday devices, such as electric motors, generators, and transformers. These principles are also used in power plants to generate electricity and in electronic circuits to regulate voltage and current.

4. Can Faraday's and Lenz's laws be applied in reverse?

Yes, Faraday's and Lenz's laws can be applied in reverse. This is known as electromagnetic induction, where a changing electric current can induce a magnetic field. This principle is used in devices such as electromagnets and inductors.

5. How do Faraday's and Lenz's laws contribute to the development of technology?

Faraday's and Lenz's laws are fundamental principles in electromagnetism and have greatly contributed to the development of technology. They have paved the way for the invention of electric motors, generators, transformers, and many other devices that we use in our daily lives. These laws also form the basis for our understanding of electromagnetism, which has led to the development of technologies such as radio, television, and wireless communication.