Induced emf: Faraday's Law and Lenz's Law Question

• predentalgirl1
In summary, the conversation discusses Faraday's Law and Lenz's Law in relation to a specific scenario. The question is about calculating the magnitude of the average emf induced in a conductive loop with specific dimensions when a uniform magnetic field drops to zero in a certain time frame. The final answer is 1.33 V, and it is confirmed to be correct by both parties involved in the conversation. Further explanation and equations are provided to support the answer and build confidence in the calculation.
predentalgirl1
[SOLVED] Induced emf: Faraday's Law and Lenz's Law Question

The plane of a conductive loop with an area of 0.020 m^2 is perpendicular to a uniform magnetic field of 0.30 T. If the field drops to zero in 0.0045 s, what is the magnitude of the average emf induced in the loop?

Given that,
Area (a) = 0.020m2
Magnetic filed (B) = 0.30 T.
When the field drops to zero,
Time taken = 0.0045 s
I have,
Induced emf = Change in flux
Time taken
= B x a cos 90
Time taken
= 0.30 x 0.020 x 1
0.0045
= 1.33 V

Is my work/answer correct?

That should be correct.

rock.freak667 said:
That should be correct.

Is it really correct...or are you just telling me that?

I calculated it the same way as you and got the same answer

$$E=\frac{BA}{t}$$

Ok...thanks. I just can't believe that I did it right. :)

$$\Phi = \iint \mathbf{B} \cdot d\mathbf{a}$$

which in a constant magnetic field perpindicular to a constant area will reduce to

$$\Phi = BA$$

Then you know that

$$\epsilon = \frac{d \Phi}{dt}$$

So the emf would be (assuming a constant change in the magnetic field)

$$\epsilon = \frac{\Delta \Phi}{\Delta t}$$

and further shows that

$$\epsilon = \frac{A * (B_i - B_f)}{(t_i - t_f)}$$

where B_f and t_f are zero.

With numbers

$$\epsilon = \frac{.02*.3}{.0045}\frac{mB}{s^2} = 1.33V$$

You need some more confidence in yourself.

Edit:
Oh right, what about Lenz's law?

Last edited:
When it comes to physics I get so confused, that's why I'm on here. lol But thanks for your help.

1. What is induced emf?

Induced emf, or electromotive force, refers to the voltage that is generated in a conductor when it is exposed to a changing magnetic field.

2. What is Faraday's Law?

Faraday's Law states that the magnitude of the induced emf is directly proportional to the rate of change of magnetic flux through a conductor.

3. How does Lenz's Law relate to Faraday's Law?

Lenz's Law is a consequence of Faraday's Law and states that the direction of the induced current in a conductor will always oppose the change in magnetic flux that produced it.

4. What is the difference between induced emf and self-inductance?

Induced emf is the voltage generated in a conductor due to a changing magnetic field, while self-inductance refers to the tendency of a conductor to resist changes in current flowing through it.

5. How are Faraday's Law and Lenz's Law applied in electromagnetics?

Faraday's Law and Lenz's Law are fundamental principles used in understanding and predicting the behavior of electromagnetic systems, such as generators, motors, and transformers.

• Introductory Physics Homework Help
Replies
7
Views
486
• Introductory Physics Homework Help
Replies
1
Views
259
• Introductory Physics Homework Help
Replies
2
Views
506
• Introductory Physics Homework Help
Replies
9
Views
2K
• Introductory Physics Homework Help
Replies
1
Views
750
• Introductory Physics Homework Help
Replies
2
Views
914
• Introductory Physics Homework Help
Replies
12
Views
352
• Introductory Physics Homework Help
Replies
7
Views
1K
• Introductory Physics Homework Help
Replies
11
Views
1K
• Introductory Physics Homework Help
Replies
4
Views
2K