ESET 211 Final Exam ;)

Two inductors L1 and L2 are connected in series. The total inductance is

a) L1+L2

b) (L1*L2)/(L1+L2)

c) (L1+L2)/(L1*L2)

d) L1*L2

Two inductors L1 and L2 are connected in series. The total inductance is

a) L1+L2

b) (L1*L2)/(L1+L2)

c) (L1+L2)/(L1*L2)

d) L1*L2

a

Two inductors L1 and L2 are connected in parallel. The total inductance is

a) L1+L2

b) (L1*L2)/(L1+L2)

c) (L1+L2)/(L1*L2)

d) L1*L2

b

When two resistors with the resistance are connected in series and a total dc voltage of 10V is applied to the two resistors. What will be the voltage cross one of the resistors?

a) 10V

b) 5V

c) 0V

d) none of the above

b

A 10 V voltage source in series with a 1 k resistor is convered to an equivallent circuit of a current source in paralle with a resistor.

The current source is 

a)  10 A

b)  1 A

c)  0.1 A

d) 0.01 A

d

A complex number 1+j1 can be written in the polar form as

a) 1 ∠ 0^o

b) 2 ∠ 45^o

c) sqrt(2) ∠ 45^o

d) 1 ∠ 45^o

c

C1= 1+j1, C2= 1+j2. Find C1/C2

a) 1/3 +j1

b) -1/3 + j1

c) 1/3 -j1

d) none of the above

d

Question 7

1 / 1 pts

(1+j1)⁴=

a) 4+j4

b)  -4

c)  4

d) none of the above

b

The complex conjugate of 1+j4 is

a) -1 + j4

b) -1 -j4

c) 1 -j4

d) none of the above

c

2 ∠ 30o=

a) 1+j2

b) sqrt(3) + j1

c) 1+ j sqrt(3)

d) none of the above

b

Conver the complex number 1/j to its polar form

a) -j

b) 1∠ 90^o

c) 1∠ -90^o

d) none of the above

c

If the frequency of an ac signal is 60Hz, then the period is 

a) 2 pi/60 sec

b) 1/60 sec

c) 60 sec

d) none of the above

b

If the frequency is 4*pi rad/s, then the period is

a) 0.5 sec

b) 2 sec

c) 2*pi sec

d) none of the above

a

Write the analytical expression for the waveform in the following figure with the phase angle in degrees.

a) v = 25 sin (377 t - 30º) V

b) v = 25 sin (377 t + 30º) V

c) v = 25/sqrt(2) sin (377 t+30º ) V

d) none of the above

b

Write the analytical expression for the waveform in the following figure with the phase angle in degrees.

a) i = 3 sin (6283 t -60º) mA

b) i = 3 sin (2000 t -60º) mA

c) i = 3 sin (6283 t +60º) mA

d) none of the above

a

Find the phase relationship between the following waveforms:
                        v = 4 sin(ωt + 50°)
                        i = 6 sin(ωt + 40°)

a) v leads i by 10 degrees

b) i leads v by 10 degrees

c) v lags i by 10 degrees

d) i lags v by 10 degrees

e) a and d

e

v =  4 cos (ωt + 20°)
i =  2 sin (ωt + 10°)

a) v leads i by 100 degrees

b) i leads v by 10 degrees

c) v lags i by 100 degrees

d) i lags v by 10 degrees

a

Find the rms value of the periodic waveform in the following figure over one full cycle.

a) 1.43

b) 0.89

c) none of the above

a

The current through a 0.1 H coil is 5 x 10¯⁶ sin(400t + 20°). What is the sinusoidal expression for the voltage?

a) v(t) =2*10^-4 sin (400t +20^o) V

b) v(t) =2*10^-4 /sqrt(2) sin (400t +110^o) V

c) v(t) =2*10^-4 sin (400t +110^o) V

d) none of the above

c

For the following pairs of voltage and currents, indicate whether the element involved is a capacitor, an indicator, or a resistor:  v = 550 sin(377t + 50°)
            i = 11 sin(377t -40°)

a) resistor

b) inductor

c) capacitor

b

Find the power factor for a circuit whose input current and voltage are as follows:
v = 60 sin(ωt + 30°)
i = 15 sin(ωt + 60°)

a) 0.654

b) 1

c) 0

d) 0.866

d

The power factor of a circuit is 0.5 lagging. The power delivered in watts is 500. If the input voltage is 50 sin(ωt + 10°), find the sinusoidal expression for the input current.

a) i=40sin(wt-50^o).

b) i= 40sin(wt+50^o).

c) i= 10sin(wt-50^o).

d) none of the above

a

When the frequency increases, the reactance of an inductor ___.

a) decreases in a linear fashion.

b) decreases in a nonlinear fashion.

c) increases in a linear fashion.

d) increases in a nonlinear fashion.

c

When the frequency increases, the reactance of an capacitor___.

a) decreases in a linear fashion.

b) decreases in a nonlinear fashion.

c) increases in a linear fashion.

d) increases in a nonlinear fashion.

b

The reactance of an inductor can be zero, but the reactance of a capacitor can never be zero.

true

If v(t) =2 sin(wt+30^o), its phasor is

a) 2∠30^o

b) 2∠120^o

c) 1.41∠30^o

d) none of the above

c

If a phsor is 2∠30^o , then the time domain function is 

a) 2 sin(wt+30^o)

b) 1.41 sin (wt+30^o)

c) 2.828 sin(wt+30^o)

d) none of the above

c

An impedance cannot be in the third quadrant, but a current through the impedance can be in the third quadrant.

true

Three impedances elements R, L, and C are connected in series. The resistance is 2 Ohms. The inductive reactance is 3 Ohms. The capacitive reactance is 3 Ohms. Find the total impedance.

a) 8 Ohms

b) 5 Ohms

c) 2 Ohms

d) none of the above

c

Three impedances elements R, L, and C are connected in parallel. The resistance is 2 Ohms. The inductive reactance is 3 Ohms. The capacitive reactance is 3 Ohms. Find the total impedance.

a) 8 Ohms

b) 5 Ohms

c) 2 Ohms

d) none of the above

c

A 1mH inductor has a 10kHz ac voltage applied to it. Find its susceptance.

a) 0.016

b) 62.8

c) none of the above

a

If an impedance element has its admittance equal to j2, then it must be 

a) a resistor

b) an inductor

c) a capacitor

d) all of the above is possible

c

If two capacitors C1, and C2 are connected in series, the total capacitence is

a) C1+C2

b) C1*C2/(C1+C2)

c) 1/C1 + 1/C2

d) (C1+C2)/C1*C2

b

Given x1=2 sin(3t+10), x2=3 sin(3t-10).

a) x1 leads x2.

b) x2 leads x1

a

If the power factor is 0, the element may be 

a) a resistor

b) a capacitor

c) an inductor

d) all the above

b or c

At high frequency, the magnitude of impedance for an inductor is 

a) very large

b) very small

c) equal to 0

d) none of the above

a

For a series RC circuit, at high frequency, its behavior is similar to

a) a capacitor

b) an inductor

c) a resistor

d) none of the above

c

The angle of an admittance is the angle by which 

a) current lags voltage

b) current leads voltage

b

If the frequency is increased, the impedance Z= 1+j2 would

a) remain the same

b) increase in magnitude

c) decrease in magnitude

d) c or d

d

Mesh Analysis is based on 

a) KVL

b) KCL

c) Voltage divider rule

d) Current divider rule

a

The balanced condition of an ac bridge networks involves __ equation(s)

a) 2

b) 1

c) more than 2

a or b

R₂ and X_L are connected in 

a) Y configuration

b) series

c) parallel

d) none of the above

c

In the circuit shown in Question 1, R1 and R2 are connected in

a) Y configuration

b) series

c) parallel

d) none of the above

d

In Question 1, what is the total impedance connected to the voltage source?

a) 26.69-j8.8 Ohms

b) 18.14 Ohms

c) 35.6+j12.4 Ohms

d) none of the above

a

If we were to write the equations for Mesh Analysis for the circuit in Question 1, how many independent loops are there?

a) 4

b) 3

c) 2

d) 1

b

The equations for Mesh Analysis should be (I₁ is the current through the 4 Ohms resistor and I₂ is current through the 8 Ohms capacitor. Z1 is the impedance of resistor. Z2 is the impedance of the inductor. Z3 is the impedance of the capacitor. )

a)  -E₁-I₁Z₁-I₁Z₂+I₂Z₂=0,    -I₂Z₂+I₁Z₂-I₂Z₃+E₂=0.

b)  E₁-I₁Z₁-I₁Z₂+I₂Z₂=0,    -I₂Z₂+I₁Z₂-I₂Z₃-E₂=0.

c)  E₁-I₁Z₁+I₁Z₂-I₂Z₂=0,    -I₂Z₂+I₁Z₂-I₂Z₃-E₂=0.

d)  E₁-I₁Z₁-I₁Z₂+I₂Z₂=0,    -I₂Z₂-I₁Z₂+I₂Z₃-E₂=0.

b

An ac voltage source V=10∠0^o (V)is connected in series with a resistor R=2 Ohms. The circuit can be converted to a current source connected to a resistor in parallel. The current source is 

a) I=10∠0^oA

b) I=0.1∠0^oA

c) I=5∠0^oA

d) none of the above

c

An ac voltage source V=10∠0^o (V)is connected in series with a resistor R=2 Ohms. The circuit can be converted to a current source connected to a resistor in parallel. The current source is:

In Question 6, the resistor connected in parallel to the current source should be

a) 2 Ohms

b) 5 Ohms

c) 0.2 Ohm

d) none of the above

a

An ac voltage source is defined as 3V1, where V1 is the voltage cross another element inthe circuit. This voltage source is called

a) CCVS

b) CCCS

c) VCCS

d) VCVS

d

If we want to do the Nodal Analysis for the circuit in Question 5, how many equation we will have?

a) 3

b) 2

c) 1

d) none of the above

c

A BTU is the amount of heat required to raise the temperature of one kg of water by one degree Celcius.

 

False

Which of the following statements are correct?

1) Energy is lated to time.

2) Power is related to time.

3) Power is related to energy.

4) Power is the same as energy.

 

2,3

If the volumes of gasoline and propoane are the same, burning gasoline will produce more heat than burning propane.

true

How much energy would be released by destruction of 0.1 gram of matter?

a) 3* 10^7 J

b) 9*10^15 J

c) 9* 10^12 J

d) 3* 10^4 J

e) none of the above

c

CUrrently, __ is used in nuclear industry to generate power.

a) Fission

b) Fusion

a

A motor can be used as a generator if the input power is switched from electrical source to mechanical source.

True

A current flows through a conductor which is placed in a meganetic field. A force is exerted on the conductor as a result.

If the current amount is doubled, and other conditions remain the same, then the force will be

a) the same

b) doubled

c) quadrupled

d) none of the above

b

A conductor is moving through a megnectic field and cutting the flux lines. A voltage will be induced. If the length of the conductor is reduced by 50% and the velocity of the conductor is increased by 100%, then the voltage induced will be

a) the same

b) doubled

c) reduced by 50%

d) none of the above

a

When using the right-hand rule to ditermine the direction of the flux lines induced by a current flowing through a straight line, the direction of the thumb is 

a) the direction of the flux line

b) the direction of the current

b

When using the right-hand rule to ditermine the direction of the flux lines induced by a current flowing through a coil, the direction of the thumb is 

a) the direction of the flux line

b) the direction of the current

a

A current-carrying conductor is in a magnetic field with a skew angle of 60 degrees. If the skew angle is changed to 0 degree while other conditions remain the same, what happend to the force applied to the conductor?

a) Force will be 0.

b) Force remain the same.

c) Force is doubled.

d) Force is reduced by 50%

c

A current-carrying conductor is in a magnetic field with a skew angle of 90 degrees. Then there will be no force applied to the conductor.

true

In a Cartesian coordinate system, the current (I) is in the positive direction of the x axis, the magnectic flux is in the positive direction of the y axis. Then the force induced is in the direction of

a) positive z axis

b) negative z axis

c) positive x axis

d) positive y axis

a

In a Cartesian coordinate system, the velocity is in the positive direction of the x axis, the magnectic flux is in the negative direction of the y axis. Then the voltage induced is in the direction of 

a) positive z axis

b) negative z axis

c) positive x axis

d) positive y axis

b

A conductor is moving in a magnectic field with constant flux density. If the alpha angle is changed from 30 degree to 90 degree, the voltage induced will

a) remain the same.

b) be doubled.

c) be reduced by 50%

d) none of the above

b

An ac motor with two poles is power by an ac votage source. If the frequency of voltage is doubled and the magnitude of the voltage is reduced by 50%, the motor speed will be

a) the same.

b) doubled.

c) reduced by 50%

d) none of the above

b

A windmill is used to drive an ac generator with two poles. The  generator is rotating at the speed of 1800 rpm, the frequency of the ac voltage generated wil be

a) 30 Hz

b) 30 rad/s

c) 120 Hz

d) 120 rad/s

a

An ac generator has 6 poles. It is rotating at the speed of 2600 rpm. Then the frequency of the votage generated is

a) 130 rad/s

b) 130 Hz

c) 260 Hz

d) 390 Hz

e) none of the above

b

A dc machine has a split ring.

true

To make a motor run in certain direction using the H brige, you need to close

a) only one switch.

b) exactly two switches.

c) exactly three switches.

d) exactly four switches.

b

H Bridge can be used to reverse the rational direction of a DC motor.

true

In the derivation of the DC Permanent Magnet motor model, the following are included in the model:

a) Resistance, Capacitance

b) Capacitance, Inductance 

c) Resistance, Inductance 

d) Resistance, Inductance,  Capacitance

c

In the derivation of the DC Permanent Magnet motor model, the following are included in the model:

a) Friction, Aerodynamic drag

b) External load, Aerodynamic drag

c) Friction, External load

d) External load, Aerodynamic drag, Friction

c

When SI units are used, the back emf gain K is

a) equal to the torque gain.

b) greater than the torque gain.

c) less than the torque gain.

d) none of the above is correct.

a

The steady state is reached

a) in the begining of motor start up.

b) when current cross the speed.

c) after the time constant (tau).

d) after sufficiently long time (> 3*tau)

 

* tau is defined as the time it takes for the speed to reach 63% of its final value.

d

Suppose the DC voltage applied to a DC motor is held constant. Which ones of the following statement are correct?

1. Motor current increases as the load torque increases.

2. Motor current increases as the load torque decreases.

3. Motor speed increases as the load torque increases.

4. Motor speed increases as the load torque decreases.

1 4

When the motor is stalled, the current reaches the maximum value.

true

A DC permanent magnetic motor with brush has R= 2 Ohms, K =0.3 (Nm/A), Tf=0.02Nm. Find the stalled current when a 6V DC voltage source is applied to the motor. 

 

a) 1 A

b) 2A

c) 3A

d) 4A

c

A DC permanent magnetic motor with brush has R= 2 Ohms, K =0.3 (Nm/A), Tf=0.02Nm. Find the stalled torque when a 6V DC voltage source is applied to the motor. 

 

a) 0.6 Nm

b) 0.88 Nm

c) 1.2 Nm

d) 2.4 Nm

b

what is that

Pressurized water reactor

This is a __ .

a) combined cycle power plant

b) combined heat and power system

c) gas power plant

d) coal-fired power plant

a

In an ac Bridge Network, Z1=1+j1, Z2=1-j1, Z3=1+j1, then Z4=

a) 1-j1

b) 1+j1

c) 2+j2

d) 2-j2

e) none of the above

a

If Nodal Analysis is used for the ac Bridge Network, how many equations do we have?

a) 4

b) 3

c) 5

d) none of the above

b

Maxwell Bridge is used for measuring

a) large inductance and small resistance

b) small capcitance and small resistance

c) large resistance and inductance

d) none of the above

c

A Y configuration of impedances with Z1=Z2=Z3=1+j1. To convert it to the Delta configuration, Z_A=Z_B=Z_C=

 

a) 3+j3

b) 1+j1

c) 1/3 + j/3

d) none of the above

a

We would like to find a Thevenin equivallent circuit between a and b (by taking out the Z_L element). Find Z_TH

a) 15-j4  Ω

b) 15+j4  Ω

c) 9.66 ∠14.93°  Ω

d) none of the above

c

Find the Isc (from a to a') for the above circuit.

a) E/(R1+R2+R3)

b) E/(R1+R2)

c) -E/(R2+R1)

d) none of the above

b

A Thevenin equivallent circuit is found to have E_TH=10+j10, Z_TH=1+j1. Maximum power can be delivered to the load when Z_L=

a) 1+j1

b) -1 +j1

c) 1-j1

d) -1-j1

e) none of the above

c

A Thevenin equivallent circuit is found to have E_TH=10+j10, Z_TH=1+j1. Maximum power can be delivered to the load when Z_L=

In Question 7, the maximu power delivered to the load would be

a) 25 W

b) 50 W

c) 100 W

d) none of the above

b

An ac power has a unit of VAR. It must be 

a) a real power

b) an average power

c) an apparent power

d) a reactive power

e) a complex power

d

An ac power has a unit of VA. It must be 

a) a real power

b) an average power

c) an apparent power

d) a reactive power

c

An ac power has a unit of W. It must be 

a) a real power

b) a complex power

c) an apparent power

d) a reactive power

a

An ac power is given as 2+j4. This is 

a) a real power

b) a complex power

c) an apparent power

d) a reactive power

b

An ac power is given as 3+j4. The apparent power must be

a) 3 W

b) 4 VAR

c)  5 VA

d) none of the above

c

An equipment has an impedance of 1+j1. A capacitor is added in parallel to the equipment for power factor correction. The reactance of the capacitor should be chosen as

a) 2 Ohms

b) 1 Ohm

c) 1/2 Ohm

d) none of the above

a

The real power delivered by the voltage source is

a) 300 W

b) 500 W

b) 900 W

d) none of the above

a

Find the total apparent power.

a) 329.6 VA

b) 538.5 VA

c) 500 VA

d) none of the above

b

For an RC Low Pass Filter, R=1 kOhms, C=0.1 micro Farads, will a signal with frequency of   2000 rad/s be blocked by this filter?

false

If R is increased and C remains the same, the RC LPF's cut-off frequency will

a) remain the same

b) increase

c) decrease

d) anything is possible

c

If R is increased by 10 times and C  takes 1/10 of the original value, the RC LPF's cut-off frequency will

a) remain the same

b) increase

c) decrease

d) anything is possible

a

If a LPF and HPF are cascaded, you will get 

a)  a pass band filter

b) an all-pass filter

c) an all-stop filter

d) a stop band filter

e) a or c

e