CH 2_BOOK_BASIC LAWS Flashcards
Does a resistor obey Ohm’s law?
Yes: A resistor is a passive element in which the voltage v across it is DIRECTLY PROPORTIONAL to the current i through it.
What is the formula for Ohm’s law?
v = iR
Is a short circuit a resistor?
Yes, with ZERO resistance.
Is an open circuit a resistor?
Yes, with INFINITE resistance.
What is the formula for CONDUCTANCE?
The CONDUCTANCE of a resistor is the ____ of its resistance?
Reciprocal
What is a branch?
A single two-terminal element in an electric circuit (such as a voltage source or resistor).
What is a node?
The point of connection between 2 or more branches.
What is a loop?
A closed path in a circuit.
A network with (b) branches, (n) nodes, and (l) independent loops will satisfy the fundamental theorem of network topology. What is this formula?
Kirchhoff’s Current Law (KCL) states that currents at any node algebraically sum to ____?
Zero
(N) Number of branches connected to the node
(i_n) nth current entering (or leaving) the node.
The sum of currents entering a node equals?
The sum of currents leaving the node.
Kirschhoff’s Voltage Law (KVL) states that the voltages around a closed path algebraically sum to ____?
Zero
(M) Number of voltages/branches in the loop
(V_m) The mth voltage
Two or more elements are in series if?
- Share a single node (that is not shared by other elements)
- Carry the same current
When elements are in series, is the current that flows through them the same or different?
The same (i_1 = i_2)
(But not the same voltage)
When are two or more elements in parallel?
- Connected to the same two nodes
- Same voltage across them
Do elements in parallel have the same voltage or current?
Same voltage, different current.
When two resistors are in SERIES, what are the formulas for their Equivalent Resistance (R_eq) and Equivalent Conductance (G_eq) ?
When two resistors are in PARALLEL, what are the formulas for their Equivalent Resistance (R_eq) and Equivalent Conductance (G_eq) ?
The VOLTAGE division principle for two resistors in SERIES is:
The CURRENT division principle for two resistors in PARALLEL is:
The formulas for a delta-to-wye transformation are:
The formulas for a wye-to-delta transformation are:
What is resistance?
Ability to resist current.
What is the formula for resistance?
p = Resistivity of material
l = Length
A = Cross-sectional area
VIEW ONLY: Resistivities of common materials.
Ohm’s Law states that the voltage (v) across a resistor is ____ ____ to the current (i) flowing through the resistor.
Directly proportional
Refer to the formula for resistance (R) and rewrite it in terms of their units.
The direction of current (i) and polarity of voltage (v) must conform with the ____ sign convention.
Passive.
When v=iR, how does current flow?
Current flows from a higher potential to a lower potential.
When v=-iR, how does current flow?
Current flows from a lower potential to higher potential.
The value of Resistance can range from ____ to ____?
Zero to infinity.
A common variable resistor is also known as a?
Potentiometer
What are the 2 common types of resistors?
a) Wirewound
b) Carbon film
What are the circuit symbols for
a) A variable resistor in general
b) A potentiometer
What are the 2 types of variable resistors?
1) Composition
2) Slider pot
Do all resistors obey Ohm’s law?
No.
A resistor that obeys Ohm’s Law is known as a ____ resistor.
Linear
What makes a resistor LINEAR?
It has a constant resistance.
What makes a resistor NON-LINEAR?
Its resistance varies with current
What is CONDUCTANCE? What is its SI unit?
Conductance is the ability of an element to conduct electric current; it is measured in mhos (℧) or siemens (S).
From the formula for conductance, what is the formula for current?
What is the formula for power in terms of resistance (R)?
What is the formula for power in terms of conductance (G)?
The POWER dissipated in a resistor is a linear or non-linear function of either current or voltage?
Non-linear
Since R and G are positive quantities, the power dissipated in a resistor is always positive. Thus, a resistor always ____ power from the circuit. This confirms the idea that a resistor is a ____ element, incapable of generating energy.
Absorbs, passive
A loop is said to be ____ if it contains at least one branch which is not a part of any other ____ loop.
Independent, independent
Referring to this illustration, rearrange the terms to show the currents entering and leaving the node.
VIEW ONLY: Parallel circuit KCL
Two circuits (or circuits in general) are said to be equivalent if they have the same ____________?
i-v relationship at a pair of terminals.
In this example, use KVL to get an equation of the voltages around the loop.
Rearrange the terms to follow the formula:
Sum of voltage drops = sum of voltage rises
What are the voltage and current formulas for resistors in series?
Voltage can also be written as v = iR_eq
The ____ ____ of any number of resistors connected in series is the sum of the individual resistors.
Equivalent resistance
Resistors in SERIES behave as:
A single resistor whose resistance is equal to the sum of the resistances of the individual resistors.
To determine the voltage across each resistor in series, we use which formula?
Referring to the Principle of Voltage, if a voltage divider has N resistors (R_1, R_2,…, R_N) in series with the source voltage (v), the nth resistor will have a voltage drop of: (Provide formula)
In an example of two resistors in parallel, observe the formulas derived for voltage and current.
What formula do we get for current in terms of voltage and equivalent resistance?
From this formula for equivalent resistance for resistors in parallel, what formula can we derive for equivalent resistance?
The Equivalent Resistance of two parallel resistors is equal to ________________?
The product of their resistances divided by their sum.
VIEW ONLY: Equivalent Resistance in parallel circuit
In parallel, R_eq is always smaller/bigger than the resistance of the smallest resistor in the circuit?
Smaller
Conductances in parallel behave as ?
A single conductance whose value is equal to the sum of the individual conductances.
The ____ ____ of resistors connected in parallel is the sum of their individual conductances.
What is the formula for G_eq?
What is the formula for the equivalent conductance G_eq of N resistors in series?
VIEW ONLY: Current Divider (series)
STILL MISSING WYE-DELTA INFO
