babuliaam

2022-09-22

A metal pipe is held vertically, and a bar magnet is dropped into it What do the electric field lines in the pipe look like as the magnet falls through it?

garnboernl

Beginner2022-09-23Added 8 answers

The approaching bar magnet generates a dipole-like magnetic field, with closed field lines that leave the north, circle around, and enter into the south.

With the bar magnet falling vertically inside the conducting cylinder, the magnetic field lines are such that, at every surface element of the cylinder, we visualize that the magnetic field vector can be decomposed into two components: one that points parallel to the surface and another that points in the radial direction with respect to the cylinder's axis.

Now, if we instead view the problem in the bar's reference frame, the cylinder is moving with the bar at rest in its center. In that case, any free positive charges q that are at any surface element of the cylinder will feel a magnetic force given by $q\overrightarrow{v}\times \overrightarrow{B}$. Thus, only the aforementioned radial components of $\overrightarrow{B}$ contribute to the magnetic force (because the parallel ones are also parallel to $\overrightarrow{v}$), and, consequently, the field lines of the magnetic force field generated around the cylinder surface are circles.

As a result, we clearly see that these magnetic force field lines seen by the bar magnet are actually electric force field lines when seen by the cylinder. Hence, the electric field lines are circles.

With the bar magnet falling vertically inside the conducting cylinder, the magnetic field lines are such that, at every surface element of the cylinder, we visualize that the magnetic field vector can be decomposed into two components: one that points parallel to the surface and another that points in the radial direction with respect to the cylinder's axis.

Now, if we instead view the problem in the bar's reference frame, the cylinder is moving with the bar at rest in its center. In that case, any free positive charges q that are at any surface element of the cylinder will feel a magnetic force given by $q\overrightarrow{v}\times \overrightarrow{B}$. Thus, only the aforementioned radial components of $\overrightarrow{B}$ contribute to the magnetic force (because the parallel ones are also parallel to $\overrightarrow{v}$), and, consequently, the field lines of the magnetic force field generated around the cylinder surface are circles.

As a result, we clearly see that these magnetic force field lines seen by the bar magnet are actually electric force field lines when seen by the cylinder. Hence, the electric field lines are circles.

The magnetic field inside a long straight solenoid carrying current

A)is zero

B)increases along its radius

C)increases as we move towards its ends

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Hertz

Watt

Newton

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Which of the following correctly describes the magnetic field near a long straight wire?

A. The field consists of straight lines perpendicular to the wire

B. The field consists of straight lines parallel to the wire

C. The field consists of radial lines originating from the wire

D. The field consists of concentric circles centered on the wireIs energy directly proportional to frequency?

What is a compass? How is a compass used to find directions?

Magnetic field lines never intersect each other because

There will be two directions of the field at the same point.

Feild lines repel each other

Field lines follow discrete paths only

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Towards 20 A

Towards 40 A

Zero

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A) 486 nm, Blue

B) 576 nm, Blue

C) 650, Blue

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Which of the following radiation has the shortest wavelength.

X-ray

Infra red

microwave

ultravioletHow to find the local extrema for $f\left(x\right)=5x-{x}^{2}$?