Chapter 2. Basic Laws of DC Circuits Flashcards
What is Ohm’s Law?
v = iR
i = v/R
R = v/i
If current flows from high potential to low potential, voltage is…
voltage is positive
If current flows from low potential to high potential, voltage is…
voltage is negative
What’s a short circuit?
connection with near zero resistance.
v = i * 0 -> v = 0
can be represented by a connecting wire
What’s an open circuit
connection with infinite resistance
i = v/ ∞ = 0
represented by an incomplete/broken path
What’s a branch?
represents a single element
What’s a node?
is point of connection between two or more branches
What’s a loop?
is any closed path in a circuit
When is a loop independent?
A loop is independent if it contains at least one branch not shared by any other independent loops
When are two elements in series?
if two elements share ONE common node, and no other element is connected
what is true about the current in elements in series?
Both elements carry the same current
When are two elements in parallel?
if they are connected to the same TWO nodes, and thus have the same voltage
Two or more series connected voltage sources can be replaced by…
one source which represents the equivalent voltage from all sources
Can voltage sources be connected in parallel?
NO, the potential difference between both nodes must be the same
Can current sources be connected in series?
NO, because the current has to be the same through one wire
Two or more parallel connected current sources can be replaced by…
one source which represents the equivalent current from the two sources
What is KCL?
What sign is current entering a node and what sign is current leaving?
states that the current entering a node must equal the current leaving a node.
current entering = negative
current leaving = positive
What is KVL?
How do we determine sign?
The sum of all voltages in a closed loop is zero
the sign on each voltage depends on which terminal is encountered first
What is the equivalent resistance for resistors in series?
equals to the sum of all individual resistance values connected in series
Req = ΣRn
What is voltage division?
allows us to calculate the voltage drop across any one resistor in a series circuit
How do we find the voltage across any one resistor in a series circuit?
(voltage division)
Vn = (Rn/ ΣR)*Vsource
the resistance we’re looking at divided by the sum of all resistors, multiplied by the voltage from the source
What is the equivalent resistance for resistors in parallel?
the voltage drop across parallel resistors are the same.
1/ Req = (1/R1) + (1/R2) + … + (1/Rn)
What should be true about equivalent resistance and the smallest resistor (in parallel resistors)
Req should always be less than the smallest resistor
How do we calculate the current across any resistors in a parallel circuit? (all resistors are parallel with each other
in = (Req/Rn)*i
i is the current source
