Electrical Engineering Refresher Exam Questions 2025
1.What is the insulation resistance when a 300-volt 30,000 ohm voltmeter
reads 230 volts across the source and 5 volts in series with the insulation?:
1.5 mega-ohms.
2.How do you determine the resistance of a 200 ft long conductor with a
diameter of 40 mils when a wire has a resistance of 1.0 ohm per 1000 ft at
a diameter of 0.1 inch?: The resistance is 2.5 ohms.
3.If two coils have an inductance of 12 mH and 6 mH with 80% coupling,
what is the mutual inductance?: 8.6 mH.
4.What is the current in mA when a capacitor is charged at 100,000
mi- cro-coulombs in 2 seconds?: 50 mA.
5.What is the equation of the line current for a coil of 50 ohm resistance
and 150 mH inductance in parallel with a 50 micro-farad capacitor at a
source voltage of 100 sin (Ît +30deg)?: 1.82 sin (tÎ - 62deg).
6.What is the outgoing current when two currents, 5+j2 and 3-j2, enter
a junction?: 2+j4A.
7.What approximate size of capacitor is necessary to raise the power
factor of a 5hp, 75% power factor, 220 volts single phase induction motor
to about 95%?: 3 kvar.
8.How much reactive power is needed to correct the power factor of a
10,000 KVA load at 85% power factor lagging to 97% lagging connected to a
13,200 volt line?: 5,156 KVAR.
9.What capacitance must be placed in series with an inductance of 0.05 H
so that at 100 Hz, the impedance equals the ohmic resistance?: 70.7 uF.
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, 10.What is the inductance of the other leg in henry if one leg of a radio
tuned circuit has a capacitance of 1 x 10^-9 farad and is tuned at 200 KHz?:
6.33 x 10^-7 H.
11.What is the reactive power of a balanced delta connected load of 4 -
j3 ohms/phase fed by a 380 V, 3-phase system?: 52 kVARS.
12.What is Van for a balanced three phase wye connected source with
nega- tive phase sequence if Vca = 398 Vrms with a 90 degrees angle?: 230
+ j 0 V.
13.What is Vbc for a balanced three phase wye connected source with
ABC phase sequence if Van = 230 Vrms with a 30 degrees angle?: 190.5 -
j330 V.
14.What is the current in each phase of a 240 V three-phase source
connected to three 10 ohm resistance loads?: 22 A, 24 A, 20 A, or 28 A.
15.In a balanced three-phase system with 10 ohm impedances and Vbc
equal to 416 V at 240 degrees, what is Icn?: 12 + j20.8 A, 12 - j20.8 A, 20.8
- j12 A, or
20.8 + j12 A.
16.What is the kva rating of a 10 kVA, 440/110 volts transformer when used
as a 550/110 volts autotransformer?: 40 kVA, 25 kVA, 12.5 kVA, or 50 kVA.
17.If a 100 kVA, 2300/230 volts transformer is used as an autotransformer
with a 3.3% impedance, what is the % impedance as an autotransformer?:
0.3%, 0.003%, 33%, or 0.033%.
18.What is the secondary winding current in amperes of a 500 hp, 2400V,
3-phase motor operated from a 13.8 kV utility service?: 157.3 A, 125.6 A,
104.9 A, or 60.6 A.
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1.What is the insulation resistance when a 300-volt 30,000 ohm voltmeter
reads 230 volts across the source and 5 volts in series with the insulation?:
1.5 mega-ohms.
2.How do you determine the resistance of a 200 ft long conductor with a
diameter of 40 mils when a wire has a resistance of 1.0 ohm per 1000 ft at
a diameter of 0.1 inch?: The resistance is 2.5 ohms.
3.If two coils have an inductance of 12 mH and 6 mH with 80% coupling,
what is the mutual inductance?: 8.6 mH.
4.What is the current in mA when a capacitor is charged at 100,000
mi- cro-coulombs in 2 seconds?: 50 mA.
5.What is the equation of the line current for a coil of 50 ohm resistance
and 150 mH inductance in parallel with a 50 micro-farad capacitor at a
source voltage of 100 sin (Ît +30deg)?: 1.82 sin (tÎ - 62deg).
6.What is the outgoing current when two currents, 5+j2 and 3-j2, enter
a junction?: 2+j4A.
7.What approximate size of capacitor is necessary to raise the power
factor of a 5hp, 75% power factor, 220 volts single phase induction motor
to about 95%?: 3 kvar.
8.How much reactive power is needed to correct the power factor of a
10,000 KVA load at 85% power factor lagging to 97% lagging connected to a
13,200 volt line?: 5,156 KVAR.
9.What capacitance must be placed in series with an inductance of 0.05 H
so that at 100 Hz, the impedance equals the ohmic resistance?: 70.7 uF.
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, 10.What is the inductance of the other leg in henry if one leg of a radio
tuned circuit has a capacitance of 1 x 10^-9 farad and is tuned at 200 KHz?:
6.33 x 10^-7 H.
11.What is the reactive power of a balanced delta connected load of 4 -
j3 ohms/phase fed by a 380 V, 3-phase system?: 52 kVARS.
12.What is Van for a balanced three phase wye connected source with
nega- tive phase sequence if Vca = 398 Vrms with a 90 degrees angle?: 230
+ j 0 V.
13.What is Vbc for a balanced three phase wye connected source with
ABC phase sequence if Van = 230 Vrms with a 30 degrees angle?: 190.5 -
j330 V.
14.What is the current in each phase of a 240 V three-phase source
connected to three 10 ohm resistance loads?: 22 A, 24 A, 20 A, or 28 A.
15.In a balanced three-phase system with 10 ohm impedances and Vbc
equal to 416 V at 240 degrees, what is Icn?: 12 + j20.8 A, 12 - j20.8 A, 20.8
- j12 A, or
20.8 + j12 A.
16.What is the kva rating of a 10 kVA, 440/110 volts transformer when used
as a 550/110 volts autotransformer?: 40 kVA, 25 kVA, 12.5 kVA, or 50 kVA.
17.If a 100 kVA, 2300/230 volts transformer is used as an autotransformer
with a 3.3% impedance, what is the % impedance as an autotransformer?:
0.3%, 0.003%, 33%, or 0.033%.
18.What is the secondary winding current in amperes of a 500 hp, 2400V,
3-phase motor operated from a 13.8 kV utility service?: 157.3 A, 125.6 A,
104.9 A, or 60.6 A.
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