Theory Practice Review.

What is the reactance of a 25 μF capacitor when the applied frequency is 400 Hz?

15.92 Ω

What is the power loss in watts of a conductor that carries 24A and has a voltage drop of 7.20V?

175W.

Two capacitors, a 20 μF and a 30 μF, are connected in series to a 400 Hz source. What is the total capacitive reactance?

33.16 Ω.

A 115/230V rated motor connected to a 230V circuit must have the windings connected in series so that each winding will receive at least 230V.

False.

Two inductors are connected in series to a 120-V, 60-Hz supply. The values of the inductors are 0.175 H and 0.255 H. The total circuit current is _____.

0.74 A

What does it cost per year (at 8 cents per kWh) for the power loss of a 12 AWG circuit conductor (100 ft long) that has a total resistance of 0.40 ohms and current flow of 16A?

$70

An inductor is connected to a 240-V, 60-Hz supply. The current in the circuit is 5 A. What is the inductance of the inductor?

.127 H work the UGLYS pg. 31 using divide instead of multiply.

A balanced 3-wire, 120/240V, single-phase circuit is connected so that the ungrounded conductors are from different transformer phases (Line 1 and Line 2). The current on the neutral conductor will be _____ percent of the ungrounded conductor current.

0% because the circuit is balanced.

An inductor is connected to a 60 Hz circuit. The inductive reactance is 75.4 Ω. What is the inductance of the inductor?

0.2 H

What is the true power of a 10A circuit operating at 120V with unity power factor?

1,200W.

The total circuit resistance of two 12 AWG conductors (each 100 ft long) is 0.40 ohms. If the current of the circuit is 16A, what is the power loss of the conductors in watts?

100W.

An inductor with an inductance of three henrys (H) is to be connected to a 60 Hz circuit. What will the inductive reactance be?

1131 Ω

Two capacitors, a 20 μF and a 30 μF, are connected in series. What is the total capacitance?

12 μF.

Two inductors are connected in series to a 120-V, 60-Hz supply. The values of the inductors are 1.5 H and 2.5 H. The total inductive reactance is _____.

1508 Ω

If the output is 1,600W and the equipment is 88 percent efficient, what are the input amperes at 120V?

15A

What is the power consumed by a 10 kW heat strip rated 230V connected to a 115V circuit?

2.50 kW.

An inductor has an inductive reactance of 12 Ω, and a wire resistance of 16 Ω. What is the impedance of the inductor?

20 Ω.

A transformer having a 208/120 three phase secondary is to supply a panelboard with a 130 amp demand load. The feeder conductors are size 1/0 AWG THWN copper. What is the max distance the panelboard can be located from the transformer so that the voltage drop does not exceed 3%

225 ft.

Determine the true power of a 7.5 amp load with a power factor of 87 percent from a three phase 208 volt source.

2350 watts

A 208/120 three phase feeder using 4 AWG aluminum conductors is to supply an 80 amp load located 100 feet from the switchboard. Determine the approximate voltage drop.

3 volts.

Two inductors are connected in parallel to a 120-V, 60-Hz supply. The values of the inductors are 0.15 H and 0.225 H. The total inductive reactance is _____.

3.54 A

A 208/120 volt 3 phase 150 amp load is located 250 feet from the main distribution switch board. What is the minimum size copper feeder conductors required to supply the load when voltage drop is limited to 3%?

3/0 AWG

A 1 μF capacitor has 2,652 Ω of reactance at 60 Hz. What is the reactance value at 400 Hz?

397.88 Ω

What is the conductor power loss in watts for a 120V circuit that has a 3 percent voltage drop and carries a current flow of 12A?

43W.

Three capacitors, a 12 μF, a 20 μF, and a 30 μF, are connected in parallel to a 60 Hz source. What is the total XC?

442.09 Ω

A 120 volt singe phase branch circuit using 12 AWG copper conductors is suppling a 15 amp load located 60 feet from the panelboard. Determine the approximate voltage drop.

4volts

Two capacitors, a 20 μF and a 30 μF, are connected in parallel. What is the total capacitance?

50 μF.

What is the reactance of a 10 pF capacitor when the applied frequency is 30 Hz?

530.52 Ω

Two inductors are connected in parallel to a 120-V, 60-Hz supply. The values of the inductors are 1.5 H and 2.5 H. The total inductive reactance is _____.

533.49 Ω

How many 20A, 120V circuits are required for forty-two, 300W incandescent luminaires (noncontinuous load)?

6 circuits

Three capacitors, a 12 μF, a 20 μF and a 30 μF, are connected in series. What is the total capacitance?

6 μF

What is the voltage drop of two 12 AWG conductors (0.20 ohms for each conductor) supplying a 16A load, located 100 ft from the power supply? Formula: EVD = I x R

6.40V

Three capacitors, a 12 μF, a 20 μF, and a 30 μF, are connected in parallel to a 400 Hz source. What is the total XC?

6.42 Ω

What is the approximate max distance a 120 volt singe phase 1800 VA load supplied with 12 AWG copper branch circuit conductors can be located from the panelboard when the permitted voltage drop is to be not more than 3%

60 feet.

An existing 208/120 volt three phase 4 wire panelboard is supplied with size 2 awg copper feeder conductors from the main switchboard. The panelboard is located 300 feet from the main. What is the max load in amps the conductors can carry without exceeding a 3% voltage drop

62 amps.

Three capacitors, a 12 μF, a 20 μF and a 30 μF, are connected in parallel. What is the total capacitance?

62 μF

Three capacitors, a 12 μF, a 20 μF, and a 30 μF, are connected in series to a 400 Hz source. What is the total XC?

66.32 Ω.

How many 20A, 120V circuits are required for forty-two, 300W luminaires (assume this is a noncontinuous inductive load) that have a power factor of 85 percent?

7 circuits.

How many 20A, 120V circuits are required for forty-two, 300W luminaires (noncontinuous load) that have a power factor of 85 percent?

7 circuits.

Two capacitors, a 20 μF and a 30 μF, are connected in parallel to a 400 Hz source. What is the total capacitive reactance?

7.96 Ω

If the output power is 1,320W and the input power is 1,800W, what is the efficiency of the equipment?

73%

An inductor has an inductive reactance of 64 Ω, and a wire resistance of 36 Ω. What is the impedance of the inductor?

73.4 Ω

What is the approximate power consumed by a 10 kW heat strip rated 230V, when connected to a 208V circuit?

8 kW.

A capacitor is connected to a 240 V supply. An ammeter indicates 3 A. What is the capacitive reactance of the capacitor?

80 Ω.

The power factor of a 5 kw load drawing 30 amps of current when connected to a 208 volt single phase source is____.

80%

A 240 volt single phase feeder with size 2/0 aluminum conductors is supplying an existing panelboard located 260 feet from the main switchboard. What is the max load that can be placed on the panel-board so that the voltage drop is limited to 3%

87 amps.

An inductor is connected to a 120-V, 60-Hz supply. The current in the circuit is 2.4 A. What is the inductive reactance?

904.8 Ω

What is the true power in watts of a 10 amp load supplied with 120 volts having a power factor of 80 percent?

960 watts

If a transformer is 97 percent efficient, for every 1 kW input, there will be _____ output.

970W.

The total resistance of a parallel circuit can be calculated by the _____ method.

equal resistance. product-over-sum. reciprocal.