Dean Summers
2022-07-23
Answered

An electromagnet was connected to a 12v battery and I verified that it was working. I then touched the electromagnet to a strong regular magnet (rated to hold over 50 kg). There was a strong force between the magnets. I then disconnected the electromagnet from power, reversed the wires, and turned it back on. I expected to feel the electromagnet repel the other magnet, but instead they two magnets got stuck together again. It seems like reversing the wires had no affect on the polarity of the electromagnet.

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Anaya Gregory

Answered 2022-07-24
Author has **14** answers

The electromagnet appears to contain a ferromagnetic core. This core is magnetized by the electromagnetic coil. It retains a magnetic field after the coil is turned off, and its field may take some time to reverse after the coil polarity is reversed.

Moreover, if the test magnet is more powerful than the coil (which sounds to be the case), it will cancel the field of the coil completely. You are essentially attaching the ferromagnet to the permanent magnet.

You might try again with only a coreless coil. Perhaps try an inductor rather than a dedicated solenoid.

Moreover, if the test magnet is more powerful than the coil (which sounds to be the case), it will cancel the field of the coil completely. You are essentially attaching the ferromagnet to the permanent magnet.

You might try again with only a coreless coil. Perhaps try an inductor rather than a dedicated solenoid.

equissupnica7

Answered 2022-07-25
Author has **4** answers

When one magnet is much stronger than another one, the stronger magnet will overcome the original magnetization (M) of the weaker magnet and attract it even when they were originally opposed.

asked 2022-05-13

Why are the electric force and magnetic force classified as electromagnetism?

I confuse the four kinds of fundamental interactions, so I think the electric force and magnetic force should not be classified as a big class called electromagnetism.

Here is my evidence:

1.The Gauss law of electric force is related to the surface integration but the Ampere's law corresponds with path integration.

2.The electric field can be caused by a single static charge while the magnetic force is caused by a moving charge or two moving infinitesimal current.

3.The electric field line is never closed, but the magnetic field line (except those to infinity) is a closed curve.

I confuse the four kinds of fundamental interactions, so I think the electric force and magnetic force should not be classified as a big class called electromagnetism.

Here is my evidence:

1.The Gauss law of electric force is related to the surface integration but the Ampere's law corresponds with path integration.

2.The electric field can be caused by a single static charge while the magnetic force is caused by a moving charge or two moving infinitesimal current.

3.The electric field line is never closed, but the magnetic field line (except those to infinity) is a closed curve.

asked 2022-04-06

Electric force vs. Magnetic force

$E$, electric field $\to $ $H$, magnetic field

$D$, electric flux density $\to $ $B$, magnetic flux density

$D=\u03f5E$ $\to $ $B=\mu H$

Electric force calculation is based on electric field: $F=qE$

But...

Magnetic force calculation is based on not magnetic field($H$) but magnetic flux density($B$):

$F=qv\times B$

What is the reason behind that? For magnetic force, why is magnetic flux density is used instead of magnetic field?

$E$, electric field $\to $ $H$, magnetic field

$D$, electric flux density $\to $ $B$, magnetic flux density

$D=\u03f5E$ $\to $ $B=\mu H$

Electric force calculation is based on electric field: $F=qE$

But...

Magnetic force calculation is based on not magnetic field($H$) but magnetic flux density($B$):

$F=qv\times B$

What is the reason behind that? For magnetic force, why is magnetic flux density is used instead of magnetic field?

asked 2020-10-20

A conducting sphere of radius 0.01m has a charge of $1.0\times {10}^{-9}C$ deposited on it. The magnitude of the electric field in N/C justoutside the surface of the sphere is:

a. 0

b. 450

c. 900

d. 4500

e. 90000

asked 2022-04-12

The Maxwell equation derived from Gauss's Law in magnetism is

$a)\oint \overrightarrow{E}.\overrightarrow{ds}=-\frac{d{\mathrm{\Phi}}_{m}}{dt}\phantom{\rule{0ex}{0ex}}b)\oint \overrightarrow{B}.\overrightarrow{ds}={\mu}_{0}I+{\u03f5}_{0}{\mu}_{0}\frac{d{\mathrm{\Phi}}_{E}}{dt}\phantom{\rule{0ex}{0ex}}c)\oint \overrightarrow{E}.\overrightarrow{dA}=\frac{{Q}_{in}}{{\u03f5}_{0}}\phantom{\rule{0ex}{0ex}}d)\oint \overrightarrow{B}.\overrightarrow{dA}=0$

$a)\oint \overrightarrow{E}.\overrightarrow{ds}=-\frac{d{\mathrm{\Phi}}_{m}}{dt}\phantom{\rule{0ex}{0ex}}b)\oint \overrightarrow{B}.\overrightarrow{ds}={\mu}_{0}I+{\u03f5}_{0}{\mu}_{0}\frac{d{\mathrm{\Phi}}_{E}}{dt}\phantom{\rule{0ex}{0ex}}c)\oint \overrightarrow{E}.\overrightarrow{dA}=\frac{{Q}_{in}}{{\u03f5}_{0}}\phantom{\rule{0ex}{0ex}}d)\oint \overrightarrow{B}.\overrightarrow{dA}=0$

asked 2021-02-02

A spherical cavity is hollowed out of the interior of a neutral conducting sphere. At the center of the cavity is a point charge,of positive charge q.

A) What is the total surface charge q on the interior surface of the conductor (i.s., on the wall of the cavity)?

C) What is the magnitude $E}_{\int$ of the electric field inside the cavity as a function of the distance from the point charge? Let k, as usual, denote $\frac{1}{4\pi {\u03f5}_{0}}$.

D)Will the total charge on the surface of the cavity change?

Will the totaly charge on the exterior of the conductor change?

Will the charge on the electric field with in the cavity change?

Will the charge on the electric field outside the cavity change?

asked 2022-05-19

I know that there is some relationship between electric current and magnetism, but I am having trouble pinning down the exact relationship. Is electric current a necessary condition for the existence of magnetic field? And is electric current a sufficient condition for the existence of magnetic field?

In other words, is it true that "there is electric current if and only if there is a magnetic field"?

In other words, is it true that "there is electric current if and only if there is a magnetic field"?

asked 2022-04-30

My question is: is earth really a magnet? Doesn anyone have any proof that earth is a magnet? Is there a magnetic core at the center of the earth? Has anyone reached the core of the earth?