named for georg simon ohm (1789-1854) · 2018. 5. 8. · » named for georg simon ohm (1789-1854)...
TRANSCRIPT
» Named for Georg Simon Ohm (1789-1854)
𝑽 = 𝑰𝑹, where V is voltage, R is resistance and I is current
*only holds when Resistance is independent of Voltage
Not a fundamental Law, meaning it only holds under certain conditions
» Ohmic: follows Ohm’s Law, using the equation the resistance of a circuit can be calculated using voltage and current
» Non- Ohmic: does not follow Ohm’s Law, equation does not work due to variable resistance that is dependent upon voltage
As current I flows through a given element in a circuit it loses voltage V in the process
» This power dissipation is found using equations:
P = I × V
or
P = I 2× R˃ Unit : Watts
Resistance: the opposition to the flow of current in an electrical wire or element
˃ Think “friction”
˃ Symbol: R
˃ Unit : Ω (Omega) Ohm, equivalent to 1V/1A
˃ Equation: 𝑹 =𝑽
𝑰
Equivalent Resistance: total resistance of a circuit based on number of components and their configuration (series or parallel)
» Series Rule: 𝑹𝑻𝒐𝒕𝒂𝒍 = 𝑹𝟏 + 𝑹𝟐 + 𝑹𝑵
» Parallel Rule: 𝟏
𝑹𝑻𝒐𝒕𝒂𝒍=
𝟏
𝑹𝟏+
𝟏
𝑹𝟐+
𝟏
𝑹𝑵
NOTE: Rules only work when circuit, or portion of a circuit are only series or only parallel
» Resistance is Dependent Upon:
˃ Length of wire/element: longer = ↑ resistance
˃ Cross-sectional area of wire/element: larger= ↓ resistance
˃ Material type: copper vs aluminum, etc.
˃ Temperature: decrease in temperature= ↓ resistance
» Gustav Robert Kirchhoff, German Physicist (1824 –1887)
» Credited with two laws essential to understanding circuits.
1. Kirchhoff's Junction Rule
2. Kirchhoff’s Voltage Rule
Rule: At any node (junction or branch point) in an electrical circuit, the sum of currents flowing into that node is equal to the sum of currents flowing out of that node
» The algebraic sum of voltages around each loop is zero
˃Beginning with one node, add voltages across each branch in the loop (if you encounter a + sign first) and subtract voltages (if you encounter a – sign first)
» Σ voltage drops - Σ voltage rises = 0
» Or Σ voltage drops = Σ voltage rises
10 V
6 V
4VLoop #1 Loop #2
Loop #3
Loop #3
4V
» Notes Circuit Resolution