A Beam of Electrons Moves at Velocity

question 69

Multiple Choice

A beam of electrons moves at velocity . The number of particles per unit volume in the beam of area A is ρ. If we imagine a cylindrical Gaussian surface of radius r and length centered on the beam, the electron flux through the surface is

• A)0.
• B)ρvf A.
• C)2ρvf A.
• D)ρvf (A+2πr ).
• E)2ρvf (A+πr ).

---

Definitions:

Consumption

The employment of goods and services by domestic units.

Savings

The portion of disposable income not spent on consumption of goods and services, set aside for future use or for investment.

Disposable Income

The financial resources available to a household for saving and spending after subtracting income taxes.

Consumption

The part of income or the amount of wealth that is used for purchasing goods and services for personal use.