Eddy Currents

carpelumen

1. Homework Statement
A magnet of mass 0.10 kg is dropped from rest and falls vertically through a 35.0 cm copper tube. Eddy currents are induced, causing the copper to warm up. The speed of the magnet as it emerges from the tube is 1.50 m/s. How much heat energy is dissipated to the environment?

2. Homework Equations
E = mgh

3. The Attempt at a Solution
h = 35 cm --> .35 m

E = (.10 kg) * (9.81) * (.35 m) = .3433 J

Is the equation incorrect?

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ehild

Homework Helper
1. Homework Statement
A magnet of mass 0.10 kg is dropped from rest and falls vertically through a 35.0 cm copper tube. Eddy currents are induced, causing the copper to warm up. The speed of the magnet as it emerges from the tube is 1.50 m/s. How much heat energy is dissipated to the environment?

2. Homework Equations
E = mgh

3. The Attempt at a Solution
h = 35 cm --> .35 m

E = (.10 kg) * (9.81) * (.35 m) = .3433 J

Is the equation incorrect?
It is the initial energy if you take the potential energy zero at the bottom of the tube. But what is the loss of energy?

ehild

NascentOxygen

Mentor
1. Homework Statement
A magnet of mass 0.10 kg is dropped from rest and falls vertically through a 35.0 cm copper tube. Eddy currents are induced, causing the copper to warm up. The speed of the magnet as it emerges from the tube is 1.50 m/s. How much heat energy is dissipated to the environment?

2. Homework Equations
E = mgh

3. The Attempt at a Solution
h = 35 cm --> .35 m

E = (.10 kg) * (9.81) * (.35 m) = .3433 J

Is the equation incorrect?
What happens to the P.E. that you have just calculated the magnet loses?

Jakob Weg

An illustrative experiment on this issue

rude man

Homework Helper
Gold Member
An illustrative experiment on this issue
Good! We note that a larger-diameter tube slows the magnet down more than a smaller-diameter one, following emf = -dΦ/dt. Also that Cu slowed the magnet down more than did Al or brass, following i = emf/R. Vielen Dank!

rude man

Homework Helper
Gold Member
1. Homework Statement
A magnet of mass 0.10 kg is dropped from rest and falls vertically through a 35.0 cm copper tube. Eddy currents are induced, causing the copper to warm up. The speed of the magnet as it emerges from the tube is 1.50 m/s. How much heat energy is dissipated to the environment?

2. Homework Equations
E = mgh

3. The Attempt at a Solution
h = 35 cm --> .35 m

E = (.10 kg) * (9.81) * (.35 m) = .3433 J

Is the equation incorrect?
That's the kinetic energy (k.e.) that would have developed in the absence of the copper tube. What was the k.e. with the tube?

"Eddy Currents"

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