Practice Test: Question Set - 03

1. A 2 mH, a 3.3 mH, and a 0.2 mH inductor are connected in series. The total inductance is
(A) 55 mH
(B) Less than 0.2 mH
(C) Less than 5.5 mH
(D) 5.5 mH

2. A 5 mH, a 4.3 mH, and a 0.6 mH inductor are connected in parallel. The total inductance is
(A) 9.9 mH
(B) Greater than 5 mH
(C) 9.9 mH or greater than 5 mH
(D) Less than 0.6 mH

3. Inductors add in parallel.
(A) True
(B) False

4. Two inductors, L1 and L2, are in parallel. L1 has a value of 25 μH and L2 a value of 50 μH. The parallel combination is in series with L3, a 20 μH coil. The entire combination is across an ac source of 60 Vrms at 300 kHz. The total rms current is
(A) 87 mA
(B) 870 mA
(C) 87 A
(D) 337 mA

5. The winding resistance of a coil can be increased by
(A) Increasing the number of turns
(B) Using a thinner wire
(C) Changing the core material
(D) Increasing the number of turns or using thinner wire

6. All coil cores are made of iron.
(A) True
(B) False

7. The current through a 120 mH coil is changing at a rate of 150 mA/s. The voltage induced across the coil is
(A) 1.8 mV
(B) 18 mV
(C) 180 mV
(D) 1.25 mV

8. Three 15 mH inductors are in series. The total inductance is
(A) 15 mH
(B) 30 mH
(C) 45 mH
(D) 5 mH

9. Faraday's law states that relative motion between a magnetic field and a coil induces a voltage across the coil.
(A) True
(B) False

10. An 18 V power supply is connected across a coil with a winding resistance of 180 Ω. Current flow in the coil is
(A) 1 mA
(B) 10 mA
(C) 100 mA
(D) 1 A

11. A 320 μH coil is in series with a 3.3 kΩ resistor. How long does it take for current to build up to its full value?
(A) 0.48 s
(B) 0.48 ms
(C) 0.48 μs
(D) 48 s

12. XL is directly proportional to frequency and inductance.
(A) True
(B) False

13. The following coils are in parallel: 75 μH, 40 μH, 25 μH, and 15 μH. The total inductance is approximately
(A) 6.9 μH
(B) 14 μH
(C) 2.2 μH
(D) 155 μH

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