Week 1 Flashcards
What is the most important quantity in electric circuits?
Charge
Define charge
A fundamental quantity of matter. Difficult to define itself, but easy to define if something has it or not
What are the symbols for charge
Q: for a constant
q: for a function
A stable atom has a net charge of _____
Zero
Define electric current
The flow of charge
What are the symbols for current
I or i
True or False: Current, in layman’s terms, is simply charge per second
True
Are electric circuits electrically neutral?
Yes, the current just moves but the charge of the entire system does not change
We only consider current caused by a flow of __________
Electrons
Does current and electron flow go in the same direction?
No, they go in opposite directions
True or False: Current is a scalar
False
True or False: Electric current is like jamming electrons in one end and immediately pulling electrons out the other end, this creates an almost instantaneous current
True
Define voltage
The potential energy of a circuit. It is the work done per unit of charge
What are the symbols for voltage?
V or v
True or False: Voltage can be measured from one point on the circuit
False, voltage must be measured between two points since work is done by applying a force across a distance
True or False: Voltage is a vector
False
Define power
The work done to charge per unit time
What is the scuffed engineering formula for power and what is the actual formula for power?
Scuffed: P=VI
Math-y: p(t)=dw(t)/dt
If power is negative, that means power ____ and is _______ the circuit
Supplies, putting power into
If power is positive, that means power is _________ the circuit
Dissipating from
Define resistance
The voltage difference required to drive a specific current through that object
What is the symbol for resistance?
R
Define capacitance
The charge stored per change in voltage
What is the symbol for capacitance?
C
Define inductance
The voltage per change in current
What is the symbol for inductance?
L
What is the SI unit for charge?
Coulomb, C
What is the SI unit for current?
Ampere, A
What is the SI unit for voltage?
Volt, V
What is the SI unit for power?
Watt, W
What is the SI unit for capacitance?
Farad, F
What is the SI unit for inductance?
Henry, H
Define circuit element
Any device wired into the circuit
Define terminal
The part of a circuit element that makes electrical contact with the rest of the circuit
Define node
An electrical connection between two or more circuit elements
Define circuit diagram
A representative schematic of the physical circuit
Define ideal wire
A path in a circuit through which an unlimited amount of current can flow with zero voltage difference
Define ideal voltage source
A two-terminal circuit element that produces a constant voltage difference between those terminals, regardless of the current that flows through it
Define ideal current source
A two-terminal circuit element that produces a constant current flowing through the terminals, regardless of the voltage difference that is across its terminals
True or False: Voltage sources are more familiar to most people than current sources. Examples include batteries and power outlets
True
If two points on a circuit are not connected by any path of wires or other circuit elements, then an __________ exists between those two points
Open circuit
If two points on a circuit are connected by at least one path that only consists of wires, then a ___________ exists between those two points
Short circuit
Define open circuit voltage
The voltage difference between two terminals when the current is zero. For a voltage source, this is the maximum voltage that can be produced
Define short circuit current
The current flowing through the terminals when the voltage difference is zero. For a current source, this is the maximum current that can be produced
True or False: An independent voltage source has a constant open circuit voltage
True
True or False: An independent current source does not maintain its short circuit current
False
Define dependent voltage source
A circuit element that has an open circuit voltage that is controlled by the voltage across, or current through, some other element in the circuit
True or False: A wire intersection is represented by a solid dot on a circuit diagram
True
True or False: A wire passing over another wire is represented by the removal of a solid dot or a small curve over the passing wire
True
Define v-i diagram
Measures the performance of a circuit element
Define Kirchhoff’s Current Law
The sum of all currents entering a node is equal to the sum of all currents leaving the node
Define Kirchhoff’s Voltage Law
The sum of all voltages around a loop is zero
Define Tellegen’s Theorem
The sum of the power dissipated in every circuit element is zero if the circuit obeys KCL and KVL
Define ground
A fictitious circuit element with only one terminal that is at a voltage of zero, and can collect or produce an infinite amount of current
Define supply
A fictitious circuit element with only one terminal that represents one terminal of a voltage source. It can collect or produce an infinite amount of current. It can only be used when a ground is also used to represent the other terminal of the voltage source. Should be labelled with the voltage V
Define the amended Kirchhoff’s Current Law (for supplies and grounds)
KCL still holds for any junction of three or more wires, but in addition an arbitrary amount of current can enter or leave a ground or supply
Define the amended Kirchhoff’s Voltage Law (for supplies and grounds)
KVL still holds for any closed loop in the circuit, but in addition, the voltage drops for all elements that connect a supply to a ground must equal the voltage of the supply (This is the “balance equation” form of KVL)
What does the v-i graph of an ideal voltage source look like?
A positive, horizontal line that does not diminish with more current
What does the v-i graph of an ideal current source look like?
A positive, vertical line that does not diminish with more voltage
