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# Tag Archives: magnet

## Magnetic Velocity

How would I figure out the velocity of a ball at the end of the chain.
For example if I had 4 half inch magnets each one 6 inches apart with 3 quarter inch steel ball behind each magnet.
If the starting velocity of the first ball to hit the magnet is 10mph.
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What if i changed the ball size half way through.
For example if I had 4 half inch magnets each one 6 inches apart with 3 1/4 inch steel ball behind the first two magnets and 3 1/8 inch steel ball behind the last 2 balls
Example video to help understand setup ## Why there is no magnetic field around a disconnected copper wire

Moving electrons produce magnetic field right? Electrons on earth are moving at an average of 27.83m/s due to earths rotation plus 30m/s due to earths revolution and may be more due to sun’s revolution and our galaxy’s revolution.
since there is no absolute motion, how can we tell if electrons are moving?
If the electrons are moving, anyway, why is there no magnetic field around a disconnected copper wire? Right hand rule is a physics principle applied to electric current passing through a straight wire, resulting in a magnetic field. The thumb points in the direction of the conventional current (from positive to negative), and the fingers in the direction of the magnetic field. (Photo credit: Wikipedia) ## Force on Current carrying conductor

“Thin and flexible wire is kept on a table in the form of a rectangle and a strong current is send through it. How will be the shape of the wire as a result?”

Answer: The parallel sides are carrying currents in opposite directions and therefore there will be repulsion between them. So, the rectangular coil will try to expand and tend to become circular.

## magnetic field

Which one we should use Bio saverts law or amperes law to find a magnetic field?

chirag

Both are used to find the magnetic field .In the case  of physical magnet Biot-Savarts law can be used

In the case of a current carrying conductor Ampers circuital law is used

## HYSTERISIS

What is hysteresis? I only know its related to the frequency.

Ans:

Hysterisis mens “Lagging Behind”

Hysteresis phenomena occur in magnetic materials, (as well as in the elastic, electric, and magnetic behavior of materials,) in which a lag occurs between the application and the removal of a field (or force) and its subsequent effect

The lack of retraceability of the magnetization curve is the property called hysteresis

#### Magnetic hysteresis When an external magnetic field is applied to a ferromagnetic substance, the atomic dipoles align themselves with the external field. Even when the external field is removed, part of the alignment will be retained: the material has become magnetized.

The relationship between magnetic field strength (H)(EXTERNAL) and magnetic flux density (B) (ACQUIRED) is not linear in such materials. If the relationship between the two is plotted for increasing levels of field strength, it will follow a curve up to a point where further increases in magnetic field strength will result in no further change in flux density. This condition is called magnetic saturation.

If the magnetic field is now reduced linearly, the plotted relationship will follow a different curve back towards zero field strength at which point it will be offset from the original curve by an amount called the remanent flux density or remanence (RETENTIVITY).

If this relationship is plotted for all strengths of applied magnetic field the result is a sort of S- shaped loop. (See the diagram) The ‘thickness’ of the middle bit of the S describes the amount of hysteresis, related to the coercivity of the material.

## Direction of magnetic field due to a current carrying conductor

“How do we know the direction of magnetic field around the current carrying conductor?” Asked Nikhil

## Resultant magnetic force

What is resultant magnetic force? can you please explain with an example.

(Shreya)

When a magnetic substance (or a magnet) is placed in a region where there are multiple magnetic fields, the net force due to all of them is called the resultant.

In other words, it is that magnetic force which can effectively replace all other magnetic force acting on it

(Need more explanation? Post as comment to this post for details)

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