Circuits 1 Exam 1

How do you determine if a circuit element is absorbing or supplying power to/from a circuit?

1) finding the current and voltage to satisfy passive sign convention, find power multiply current and voltage

add conductances in series

1/Geq = 1/G1+1/G2

a typical household electrical circuit is about how many amps?

15-20 A (110V)

t f when performing nodal analysis, it is necessary and advisable to define a notation for every current entering or leaving each node.

FALSE this is unneccessary

t f the voltage at the positive end of a 6.2 V source is necessarily 6.2 V

False! voltage sources only establish voltage differences, not absolute; this only applies if the negative end is connected to agnd

t f the recommendend "final" ar that should appear in the equations resulting from nodal analysis include node voltages and all control variales for dependent sources

False. the control variables should preferrably be eliminated, leaving only node voltages.

add conductances in parallel

Geq = G1 +G2

relations between the following units J N s m Kg C V W Ohm A S

J=N*m=kg*m^2/s^2 N=kg*m/s^2 J= C*V=W*s S=1/Ohms=A/V A=C/s V =Ohms*A W=V*A=J/s

which type of analysis leads to matrix equations?

NODE AND MESH

power is positive

absorption of power

the voltages of two current sources in series

add algebraically

the voltages of two voltage sources in series-->

add algebraically

Give a precise statement of Thevenin's theorem

any linear, time-invariant, resistive circuit is equivalent at its terminals to the parallel combination of an ideal current source and a resistor (the Thevenin equivalent resistance).

precise statement of Norton's theorem

any linear, time-invariant, resistive circuit is equivalent at its terminals to the parallel(//) combination of an ideal current source and a resistor(the thevenin equivalent resistance)

In a lightning storm, why are you safe in a car

because you are not grounded

superposition,

can't sum the current or voltage from an alone dependent source

unit names are not capitalized, ever ever ever

coulombs amperes siemens joule

superposition can only be used to find

current and voltage, NOT POWER

current enters a junction and splitts off, is it true that more current will flow through the smaller resistor?

false, it depends on what is connected further downstream.

t or f, can kill dependent sources

false, only kill independent sources

A linear relationship must have two properties, called ____ and ____. (both end ity)

homogeneity, and additivity

precise statement of Superposition theorem

in any linear, time-invariant resistive circuit, we can find any voltage or current in the circuit by summing the corresponding voltages or currents that are caused by each independent source acting separately (after "killing" all other independent sources)

what is the value of Rth for an ideal CURRENT source?

infinite! ∞∞∞∞

A good voltemeter has a high _______ _____.

input impedance

a good current meter has a low ____ _____.

input impedance

what must be true about a voltage source to apply SOURCE TRANSFORMATION

it must have a finite resistor in series with it, if the series resistance is zero, can't be transformed

discuss: a 10kOhm resistor dissipates more power than a 1kOhm resistor

may or may not be true; if they both have the same voltage, the smaller resistor dissipates more power (V^2/R). if they both have the same current, the larger resistor dissipates more power (I^2R)

the currents of two current sourses in series

must be the same

the currents of two voltage sources in series -->

must be the same

when applying KVL to sum voltage drops, we conventionally add a minus sign to the value of a voltage source when the direction we are following leads us into the

negative terminal, and the terms across the resistors are positive

Units for the gain of: current-controlled VS voltage-controlled CS current-controlled CS voltage-controlled VS

ohms siemens dimensionless dimensionless

Mesh analysis is restrictive to what kind of circuits?

planar circuits, because no wires are crossing

what must be true about a current source to apply source transformation

resistor connected in // with it . CANNOT BE TRANSFORMED IF // RESISTANCE IS ∅

I-V relationships showing linearity

see chart

when breaking a circuit to use Thevenin's theorem to solve it, NEVER do what?

separate a controlled source from its controlled variable.

two elements in ____ must have the same current

series

a short circuit implies zero ____. an open circuit implies zero ____.

sht ckt zvoltage, opnckt z eroc urrent

power is negative

supplying power

T n G p k m u f M a

tera=10^12 nano=10^-9 giga=10^9 pico=10^-12 kilo=10^3 mili=10^-3 femto=10^-15 micro=10^-6 atto=10^-18 Mega=10^6

Precise statement of KCL

the algebraic sum of all currents leaving or entering a node (or any other closed surface) in a circuit is zero

precise statement of KVL

the algebraic sum of all voltage drops or rises around a closed loop in a circuit (which need not run entirely through conductors or circuit elements) is zero

when dependent sources are present and we are doing mesh or node analysis, the control variables for the dependent sources must be expressed in terms of what, exactly?

the node voltages, in nodal analysis the mesh currents, in mesh analysis

t f the thevenin equivalent circuit of one with a dependent source could have a negative Rth

true

two elements in parallel must have the same ____

voltage (parallel has l's, so does voltage)

the voltage across an ideal current source is _____

whatever it needs to be to maintain the current at a fixed value

the current through an ideal voltage source is

whatever it needs to be to maintain the voltage at a fixed value

explain exactly when you need to use supernode when doing nodal analysis

when there is a voltage source with neither end connected to ground

when is it necessary to use a test source at the terminals of a circuit to find its norton equivalent circuit?

whenever the circuit has no independent sources, when short-circuit current is zero and open circuit voltage is zero

explain when need supermesh in mesh analysis

whenever there is an internal current source(shared by two loops)

what is the value of Rth, for an ideal voltage source?

zero