# ENT 342 exam II

 The square root of -1 is the symbol i or j i*i or j*j is -1 i^3 or j^3 is -j i^4 or j^4 is 1 A complex number is like a 2D vector Complex numbers are frequently used in electrical engineering The number (3+j4) is an example of a _______ number complex The real part of 3+j4 is 3 The imaginary part of 3+j4 is 4 The magnitude of 3+j4 is 5 The angle of 3+j4 is 53.13 deg The sum of 3 and j4 is 3+j4 The magnitude of the sum of 3 and j4 is 5 The angle of the sum of 3 and j4 is 53.13 deg or 0.927 rad exp(1) is 2.71828 exp(j*pi) is -1 exp(-j*pi) is -1 exp(-j*pi/2) is -j The sum of 3 and j4 is exp(0.927j)*5 5*exp(0.927j) both of these Complex numbers can be all of these multiplied and divided added and subtracted raised to powers placed in matrices exp(j*z) is the same as cos(z)+j*sin(z) sin(z), cos(z), tan(z), ln(z), log(z) _____ when z is a complex number are defined AC voltage of 5*exp(j53.13 deg) has an amplitude of 5 volts AC voltage of 5*exp(j53.13 deg) has an phase of 53.13 degrees Video H342510 has an error at time 4:56 where the ramp function is missing. true The mathematically rigorous version of a complex number in polar form is (exp(-i*G)*A) where G is in radians A complex number in polar form looks like (exp(-i*G)*A) if G is expressed in radians A complex number in polar form looks like (A/_G) if G is expressed in degrees The poles of F(s)=N(s)/D(s) are also the roots of the polynomial: D(s) The possible number of different types of poles of F(s) in this course is 3 The inverse Laplace Transform of F(s) contains f(t)=A*exp(K*t)*sin(w*t+M) for each complex conjugate pair of poles The inverse Laplace Transform of F(s) contains f(t)=A*t*exp(-H*t) + C*exp(-H*t) for each pair of repeating real poles The inverse Laplace Transform of F(s) contains a term f(t)=A*exp(-B*t) for each pair of repeating real poles The inverse Laplace Transform of F(s) contains a term f(t)=A*exp(-B*t) for each non-repeating real pole Can M be expressed in degrees in f(t)=A*exp(K*t)*sin(w*t+M)? frequently is, but never in a calculation The radian phase shift of f(t)=A*exp(K*t)*sin(w*t+M) is M The radian/second frequency of f(t)=A*exp(K*t)*sin(w*t+M) is w The function f(t)=A*exp(K*t)*sin(w*t+M) is called sinusoidal modulated by an exponential function The function f(t)=A*t*exp(-H*t) + C*exp(-H*t) is called exponential plus another exponential component modulated by a ramp The function f(t)=A*exp(-B*t) is called exponential If B is negative in the function f(t)=A*exp(-B*t), then the time constant does not exist, because the function is unstable The time constant in f(t)=A*exp(-K*t)*sin(w*t+M) is 1/K. 1/K In this stable function, f(t)=A*exp(K*t)*sin(w*t+M), K is always negative The time constant of both terms in f(t)=A*t*exp(-H*t) + C*exp(-H*t) 1/H The time constant in f(t)=A*exp(-B*t) is 1/B Delta functions closely approximate real-world situations. true Delta functions are theoretical and extremely practical . 6*delta(t) has a height of _____ and width of _____ and an area of ____. infinity, zero, 6 A unit delta function has a height of _____ and width of _____ and an area of ____. infinity, zero, one A delta function has a height of _____ and width of _____. infinity, zero If F(s) is a constant, the inverse Laplace transform f(t) is a delta function Long division can be performed on polynomials by the TI-89 using the function propFrac(N(x)/D(x)) Proper N2(s)/D(s) in F(s)=P(s)+N2(s)/D(s), and N2(s) is a function of s Proper N2(s)/D(s) in F(s)=P(s)+N2(s)/D(s), and P(s) is a constant or a function of s Proper N2(s)/D(s) in F(s)=P(s)+N2(s)/D(s) is derived from improper F(s)=N(s)/D(s) by dividing D(s) into N(s) For improper F(s)=N(s)/D(s), proper F(s)=P(s)+N2(s)/D(s) is where the degree of ___ is less than the degree of ____. N2(s), D(s) F(s) = N(s) / D(s) is improper when the degree of ___ is greater or equal to the degree of ____. N(s), D(s) The improper fraction 13/4 can be made proper by division and is equivalent to 3 plus 1/4 1/j -j The impedance in Ohms of a capacitor is _____ Ohms. 1/(jwC) -j/(wC) all of these (1/C)/(jw) The impedance in Ohms of an inductor is _____ Ohms. jwL The impedance in Ohms of a resistor is _____ Ohms. R Use the s-domain instead of the jw-domain, because the s-domain yields both transient and steady state solutions Use the jw-domain instead of the s-domain only in steady state conditions To transform from the s-domain to the jw-domain, replace s with j*w. true, it is that easy. Derivative in the time domain is equivalent to ______ in the s-domain. multiplication by s The Laplace transform of i'(t)=(d/dt)i(t) is s*I(s) The Laplace transform of v'(t)=(d/dt)v(t) is s*V(s) IV relationship for a resistor is _____ in the time domain. an algebraic equation IV relationship for an inductor or capacitor is _____ in the time domain. an algebraic equation IV relationship for an inductor or capacitor is _____ in the time domain an ordinary differential equation Impedance of a resistor, capacitor, and inductor are derived from the ____ of each. current voltage relationship Definition of impedance is Z(s)= V(s)/I(s) The impedance in Ohms of a capacitor is _____ Ohms. 1/(sC) = (1/C)/s The impedance in Ohms of an inductor is _____ Ohms. sL The impedance in Ohms of a resistor is _____ Ohms. R complex number with Ohms units is called impedance (A angle(B)) = A*exp(j*B) true because A*exp(j*B) is mathematically rigorous The complex number (A angle(B)) represents the sinusoid A*sin(wt+B) A complex number that represents a sinusoid is called a phasor Y=1/Z and Z=1/Y, therefore R=1/G and G=1/R false The relationship between Z and Y is inverse In Y = G + jB, Y is ____; G is ____; B is ____, all in units of Siemens. adimttance, conductance, susceptance In Z = R + jX, Z is ____; R is ____; X is _____, all in units of Ohms. impedance, resistance, reactance A*(1 at -180 deg) = -A A*(1 at 180 deg)*(-1) = A A*(-1)*(-1) = A (-1 at 0 degrees) is a complex number equal to -1 1 at -180 degrees) is a complex number equal to -1 (1 at 180 degrees) is a complex number equal to -1 V1=(10 at -20 degrees) volts and V2=(50 at -60 degrees) volts. V1 ____ V2 by ____. leads, 40 degrees V1=(10 at 20 degrees) volts and V2=(50 at 60 degrees) volts. V1 ____ V2 by ____. lags, 40 degrees Steady state AC circuit analysis uses _____ techniques as for DC circuits. THE SAME jw-domain impedance in Ohms of an inductor has an angle of 90 degrees jw-domain impedance in Ohms of a capacitor has an angle of -90 degrees jw-domain impedance in Ohms of a resistor has an angle of 0 A phasor is a complex number representing a sinusoidal voltage or current After 1 second, V(t)=-12exp(-4t)+13.4sin(2t+1.107) will be sinusoidal The transient in V(t)=-12exp(-4t)+13.4sin(2t+1.107) will be 98.2% complete at t=_____ second(s). 1 e steady state part of V(t)=-12exp(-4t)+13.4sin(2t+1.107) is 13.4sin(2t+1.107) The transient part of V(t)=-12exp(-4t)+13.4sin(2t+1.107) is -12exp(-4t) V(t)=-12exp(-4t)+13.4sin(2t+1.107) is the voltage across the inductor in an RL circuit containing switch and 30sin(2t) voltage source in H342540 video true V(t)=-12exp(-4t)+13.4sin(2t+1.107) is the voltage across the inductor in an RL circuit containing switch and 30sin(2t) voltage source in H342540 video Kirchhoff's voltage law In V=(10 at 20 degrees) volts, is the phasor representation of v(t)=10*sin(w*t+20deg) volts In I=(10 at 20 degrees) amps, is the phasor representation of i(t)=10*sin(w*t+20deg) amps In Z = 30 - j40, the impedance angle is _____ degrees  -53.13 In Z = 30 + j40, the impedance angle is _____ degrees 53.13 In Z = 30 - j40, the impedance magnitude is ____ Ohms 50 In Z = 30 + j40, the impedance magnitude is ____ Ohms 50 In Z = 30 - j40, 40 Ohms is ______ reactance of 40 Ohms capacitor In Z = 30 + j40, 40 Ohms is ______ reactance of 40 Ohms inductor In Z = R + jX, X in Ohms is reactance In Z = R + jX, Z in Ohms is impedance In Z = R + jX, R in Ohms is resistance Square root of the average of a function squared is the same as RMS. true In S = 3 + j4, apparent power=_____, power=_____, and reactive power=_____. 5 VA, 3 Watts, 4 VARs V*conj(V)/(2*conj(Z)) sto-> apvz(V,Z) creates a TI-89 function for complex power in terms of phasor voltage and jw-domain impedance. true, if the "*" means multiply I*conj(I)*Z/2 sto-> apiz(I,Z) creates a TI-89 function for complex power in terms of phasor current and jw-domain impedance. true, if the "*" means multiply . V*conj(I)/2 sto-> apiv(I,V) creates a TI-89 function for complex power in terms of phasor current and voltage true, if the "*" means multiply The "2" in S=VI^*/2 occurs when the phasor voltage or current amplitude is peak value If phasor voltage or current were defined using the RMS value instead of the peak value, then complex power would be S=VI^* S = V multiplied by I^* divided by 2 (S=VI^*/2) is analogous to the DC power formula (P=IV). true, when the "^*" means complex conjugate If A is a phasor, then A^* is complex conjugate of A true Complex conjugate of A+jB is A-jB Unity power factor (PF=1) is desirable because current is minimized Unity power factor (PF=1) occurs when Q=0 In the power triange for S = P + jQ, _____ is the power factor (PF). cos(theta) . In the power triangle for S = P + jQ, sin(theta) = |Q|/|S| cos(thata) = P/|S| tan(theta) = |Q|/P all of these An resistor exchanges power in an AC circuit by absorbing power from the circuit and returning that power to the circuit every cycle. false An inductor exchanges power in an AC circuit by absorbing power from the circuit and returning that power to the circuit every cycle. true A capacitor exchanges power in an AC circuit by absorbing power from the circuit and returning that power to the circuit every cycle. true In complex power S = P + jQ, Q is power in VARS that is exchanged In complex power S = P + jQ, P is power in watts that is _______. dissipated or supplied Complex power is S = P + jQ, and Q is NEGATIVE, then Q is capacitive Complex power is S = P + jQ, and Q is POSITIVE, then Q is inductive The mathematical expression for complex power is S = P +- jQ where S is ____ and "+-" means plus or minus. apparent power in volt-amps (VA) The mathematical expression for complex power is S = P +- jQ where Q is ____ and "+-" means plus or minus. reactive power in VARS The mathematical expression for complex power is S = P +- jQ where P is ____ and "+-" means plus or minus. power in watts Complex power has units of watts all of these volts-amps-reactive (VARS) volt-amps Authorlacythecoolest ID318824 Card SetENT 342 exam II DescriptionENT 342 exam II preclass quiz ?'s Updated2016-04-12T10:48:23Z Show Answers