Deflection A beam of electrons in a cathode-ray tube...

Deflection A beam of electrons in a cathode-ray tube approaches the deflecting magnets. The north pole is at the top of the tube; the south pole is on the bottom. If you are looking at the tube from the direction of the phosphor screen, in which direction are the electrons deflected?

Key Concepts

Lorentz Force

This is the force experienced by a charged particle moving in a magnetic (and/or electric) field. It is given by F = q(v × B) and is responsible for the deflection of moving charges like electrons. Understanding this force is fundamental to predicting the motion of charged particles in fields and forms the basis for many devices including cathode?ray tubes.

Magnetic Field

A magnetic field exerts a force on moving charges that depends on the field's direction and magnitude. The field is typically depicted as having a direction, running from the magnet's north pole to its south pole. In the context of deflection, correctly identifying the field direction is critical to determining the resultant force on a charged particle.

Right-Hand Rule and Negative Charge Considerations

The right-hand rule is a mnemonic for figuring out the direction of the force on a positive charge moving in a magnetic field (via the cross product of velocity and magnetic field vectors). However, since electrons carry a negative charge, the actual force on them is opposite to the direction predicted by the right-hand rule. This reversal is crucial for determining the correct deflection direction in devices like cathode-ray tubes.

Cathode-Ray Tube (CRT) Deflection

In a cathode-ray tube, electrons are accelerated and then deflected by magnetic fields to hit specific locations on a phosphor screen. The arrangement and orientation of the deflecting magnets, along with the negative charge of electrons, determine how and in which direction the beam will deflect. Understanding CRT operation involves applying the Lorentz force, the vector cross product, and considering the sign of the electron charge.

Transcript

Please give Ace some feedback