Zero Induced EMF: Find Rate of B Change for Problem 9

• CD135
In summary, the question is about finding the rate at which the magnetic field B should change in order to induce no emf in the circuit when wire AB is at a distance of 5.00 cm from the left end of the loop. This can be solved by equating the emfs caused by the motion of the wire and the change in magnetic field. The given information about the velocity, length, and magnetic field in problem 9 is also needed for the solution.
CD135

Homework Statement

Question I need help with: If wire AB of problem 9 moves with a velocity of 50.0 m/s to the right, at what rate should B change when the wire is at a distance of 5.00 cm from the left end of the loop, such that there will be no induced emf in the circuit? Answer: 300 T/s

Problem 9: (I don't know if this information is needed to solve the question above so I'm listing it here anyway)
The wire AB in the diagram moves to the right with a velocity of 25.0 cm/s. If l = 20.0 cm, B = 0.300 T, and the total resistance of the circuit is 50.0 Ω, find (a) the induced emf in wire AB, (b) the current flowing in the circuit, and (c) the direction of the current.Diagram is attatched

Homework Equations

emf=Blv
emf=change in flux/ change in time

The Attempt at a Solution

I don't understand this question. I have been trying for a very long time and I am very lost. If there is a velocity, electric field, and length, how could there ever be zero induced EMF? I was able to get question 9 as emf=Blv, very straight forward and I understand how the equation is derived. I'm clearly missing something here but I cannot figure out what.

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Any help would be appreciated. I cannot find any information online or in the textbook to help me come up with any sort of solution. Thank you in advance!

CD135 said:
emf=Blv
emf=change in flux/ change in time
These two emfs will be opposing each other such that resultant emf will be 0.
Write mathematical equations for each and simply equate them.
CD135 said:
at what rate should B change
This asks you about 'rate of change' of magnetic field. Ring any bells?
CD135 said:
Right.

CD135 said:
(I don't know if this information is needed to solve the question above
CD135 said:
l = 20.0 cm, B = 0.300 T
This is needed.

1. What is zero induced EMF?

Zero induced EMF refers to the absence of an electromotive force (EMF) in a circuit. This means that there is no change in magnetic flux and therefore no current induced in the circuit.

2. How is the rate of change of magnetic field (B) calculated?

The rate of change of magnetic field (B) can be calculated using the formula B = μ0I/2πr, where μ0 is the permeability of free space, I is the current, and r is the distance from the current. In this case, we are finding the rate of change for a specific problem, so the values for μ0, I, and r would be provided in the problem.

3. What is Problem 9 referring to?

Problem 9 is likely referring to a specific question or scenario that involves calculating the rate of change of magnetic field (B) for a given situation. This could be a question on a homework assignment or a problem in a textbook.

4. What is the significance of finding the rate of change of magnetic field (B) in this problem?

The rate of change of magnetic field (B) is important in understanding the behavior of electrical circuits and electromagnetic phenomena. It can help determine the strength of induced currents and the effects of changing magnetic fields on a circuit.

5. Are there any real-world applications of zero induced EMF?

Yes, zero induced EMF can be observed in situations where there is no relative motion between a conductor and a magnetic field. This can occur in stationary conductors, such as in a transformer core, or in situations where the magnetic field is constant, such as in a DC motor.

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