PHYS 1750: SELECTED TOPICS in PHYSICS
LECTURE 31. Currents, Resistance, and Power
19.1. | Electric Current | ||
1. | Total flow of charge I = Q /Δ t | ||
2. | Ampere = Coulomb/second | ||
3. | Pos = positive charge/second | ||
4. |
Charge in volume Q = n*A*Δ x*q n = number of charges / unit volume A = cross section area of current flow Δ x = length of current flow q = charge value of charge carriers (electrons) | ||
5. | Δ x = v*Δ t; v = drift velocity | ||
6. | I = n*q*v*A | ||
19.2. | Resistance R | ||
1. | Ohm's law: Δ V = IR | ||
2. | Ohm = Volt/Ampere = Joule*second | ||
19.3. | Resistivity ρ (bulk property) | ||
1. | R = ρ*L /A | ||
2. | Materials (Table 19.1) | ||
19.4. | Energy and Power | ||
1. | P = IV | ||
2. | P = I 2R | ||
3. | P = V 2/R |