Rate of Magnetic Field Change and current

AI Thread Summary
To induce a current of 0.39A in a conducting loop with an area of 7.2×10−2 m² and a resistance of 120 ohms, the rate of change of the magnetic field must be calculated. The relevant equation for electromotive force (emf) is emf = -dΦ/dt, where Φ represents the magnetic flux. The initial attempt incorrectly applied the formula for emf and did not account for the need to calculate magnetic flux first. The user realized the mistake in interpreting the magnetic field as flux, leading to confusion in the calculations. Understanding the distinction between magnetic field and magnetic flux is crucial for solving the problem correctly.
ihearyourecho
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Homework Statement



A single conducting loop of wire has an area of 7.2×10−2m2 and a resistance of 120 ohms. Perpendicular to the plane of the loop is a magnetic field of strength 0.50 T.

At what rate must this field change if the induced current in the loop is to be 0.39A?

Homework Equations



emf=(-NdeltaIB)/(deltat)
Rate of change = emf/-N

The Attempt at a Solution



emf=(-NdeltaIB)/(deltat)
Rate of change = emf/-N

It's a single loop, so N should be 1
Rate of change - emf/-1

emf=v=IR

Rate of change = -IR
Rate of change = -(.39A)*120ohms=-46.8

This isn't right though.

Thanks for the help :)
 
Last edited:
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anyone? :)
 
ihearyourecho said:
emf=(-NdeltaIB)/(deltat)

The correct equation is

emf = - dΦ/dt

where Φ is the magnetic flux through the loop which you need to calculate first.
 
Arggh, I've been reading it as magnetic field, not flux. Thanks!
 

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