EET 3086 Final Exam

A capacitor with a reactance (XC) of 1.2 kΩ is in series with a 1 kΩ resistor. The combination is across a sine wave ac source producing 20 mA. The phase angle (θ) of the source voltage, using current as a reference, is

-50.2°

A voltage source (VS) with 30 Ω of internal resistance (RS) has a no-load output of 15 V. The voltage across the load (VL) when the load resistor (RL) is 1 k Ω is

0 V

Which of the following AWG wire sizes has the largest current-carrying capacity?

0000

A bar magnet has five lines of force cutting one square centimeter (1 cm2). Assuming that each line of force represents 30 μWb of flux, the flux density for the magnet is

1.5 T

A circuit consists of two opposing voltage sources: a VA of 15 V and a VB of 9 V. There are three resistors: an R1 of 27 Ω, an R2, of 16 Ω, and an R3 of 8 Ω. One end of R1 is connected to the + side of VA while one end of R2 is connected to the + end of VB. The remaining leads of R1 and R2 are connected together along with one end of R3. The other end of R3 is connected to the negative end of both VA and VB. The voltage across R1 is

10.03 V

A parallel RL circuit has a reactance of 1.8 kΩ and a resistance of 470 Ω. The phase angle of the circuit impedance is

14.6°

The resistance of a 35 cm length of copper with a cross-sectional area of 0.03 cm2 is

2 mΩ

The wavelength (in meters) for a 140 MHz sine wave is

2.14 m

A resistor is connected across a 50 V source. What is the maximum current possible in the circuit if the resistor is color-coded at red, orange, orange, silver?

2.42 mA

A 40 mH coil with an XL of 2.2 kΩ is in series with a 10 kΩ resistor, the combination of which is across a 12-V sine wave ac signal source. The voltage across the inductor is

2.57 V

A capacitor circuit carrying 12 mA is placed across a 9-V sine wave ac source. In parallel with the capacitor is a resistor carrying 20 mA. The total circuit current is

23.3 mA

One complete cycle of a waveform occupies 4 major vertical divisions on an oscilloscope display. If the time base is set at 1 ms/div, the frequency of the waveform is

250 Hz

The value code on a certain capacitor is 33. What is its rated capacitance?

33 pF

A square wave has a pulse width (PW) of 60 μs and a cycle time (TC) of 140 μs. The duty cycle is

42.86%

An RC circuit has measured values of VS = 14 Vac, IS = 5 mA, and θ = -35°. The amount of power dissipated by the circuit is

57 mW

A capacitor with a reactance (XC) of 1.2 kΩ is in series with a 1 kΩ resistor. The combination is across a sine wave ac source producing 20 mA. The apparent power (PAPP) for the circuit is

625 mVA

The guaranteed range of measured values for a 68 kΩ resistor with a 5% tolerance is

64.6 kΩ minimum; 71.4 kΩ maximum

A circuit consists of two resistors in series, an R1 of 470 Ω and an R2 of 680 Ω, across a 24-V source. An RL of 68 Ω is placed across R2. The values of VL and VNL are

VL = 2.79 V, VNL = 14.19 V

Increasing the value for L, alone, in a parallel RL circuit causes

XL to increase

Increasing the value for f, alone, in a parallel RC circuit causes

ZT to increase

A sine wave with a dc offset has

a full-cycle average that is not equal to zero unequal positive and negative peak value an average value that is equal to the value of the dc offset

In order to impedance match a high-impedance load to a low-impedance source you would use a(n)

a step-up transformer

Which is not a common cause of loss of magnetic strength for a permanent magnet?

allowing the magnet to be jarred or dropped

Which type resistor is most commonly found in high-power electrical applications?

carbon-composition resistor

A capacitor and a resistor are in series across a dc source. When the capacitor is fully charged,

current is zero

Increasing the frequency in a series RL circuit causes the power factor to

decrease

In a dual dc power supply, the terminal that is common to both voltage sources, is the

ground terminal

The ability of a material to retain its magnetic characteristics is called

retentivity

In order to measure current

you must install the meter in the current path

Increasing the value for C, alone, in a parallel RC circuit causes

θ to decrease

An ac sine wave has a frequency of 25 kHz. The time from the start of the cycle until the θ = 140° point on the waveform is

≅ 15.6 μs

A capacitor with an XC of 500 Ω is across a sine wave ac source of 10 V. In parallel with the capacitor is a 300 Ω resistor. The magnitude of ZT for the circuit is

≅ 257 Ω

Two coils, an L1 of 10 mH and an L2 of 15 mH, are connected series-aiding across a sine wave ac source. The coefficient of coupling (k) is 0.9. The total inductance is

≅ 47 mH