About Inductance

What is inductance and how does it work? This is a question that many people have, but don't know where to find the answer. In this post, we will discuss inductance and its effects on electronics. We will also provide a few examples of inductance in action. By the end of this post, you will have a better understanding of inductance and how it affects your everyday life!

Inductance is a property of an electronic circuit that opposes changes in current. It is measured in henries (H). The unit of inductance was named after Joseph Henry, who discovered inductance while investigating the nature of electricity.

Inductance occurs when there is a change in the magnetic field around a conductor. This changing magnetic field inducts or "creates" a voltage in the conductor. The magnitude of this voltage is proportional to the rate of change of the magnetic field and is given by the equation:

V = L di/dt

where V is the voltage, L is the inductance, and di/dt is the rate of change of current.

The inductance of a circuit is typically created by the presence of inductors. Inductors are devices that have inductance, which is used to oppose changes in current. They are made of a conductor (usually a coil of wire) that surrounds a magnetic material (such as iron). The inductance of an inductor is proportional to the number of turns in the coil and the area of the coil.

Inductors are used in a variety of electronic devices, including radios, TVs, computers, and cell phones. They are also used in power supplies and inductive charging systems.

The inductance of a circuit can also be affected by the presence of other inductors in the vicinity. This is called inductive coupling. Inductive coupling occurs when the magnetic field of one inductor induces a voltage in another inductor. The amount of inductive coupling between two inductors is proportional to the amount of inductance in each inductor and the distance between them.

Following are some of the multiple choice questions on the Inductance with answers that will help the students in developing their knowledge.

Inductance MCQ

1. Which of the following are units for inductance?I. HenryII. Joules/(Ampere)2III. Volt . second/Ampere

  • II only
  • III only
  • I and II only
  • I, II and III

2. Which of the following is the total series capacitive reactance formula?

  • XCT = XC1 * XC2 * XC3....
  • XCT = XC1 - XC2 - XC3...
  • XCT = XC1 + XC2 + XC3...
  • XCT = 1/[(1/XC1) + (1/XC2) + (1/XC3) ...]

3. A 10-turn ideal solenoid has an inductance of 3.5 mH. When the solenoid carries a current of 2.0 A the magnetic flux through each turn is:

  • 0 Wb
  • 3.5 x 10^–4 Wb
  • 7.0 x 10^–4 Wb
  • 7.0 x 10^–3 Wb

4. Which component opposes any change in current?

  • Diode
  • Transistor
  • Inductor
  • Capacitor

5. An airplane with a wingspan of 60.0 m flies parallel to the Earth’s surface at a point where the downward component of the Earth's magnetic field is 0.400 x l0-4 T. If the induced potential between wingtips is 0.900 V, what is the plane’s speed?

  • 250 m/s
  • 338 m/s
  • 375 m/s
  • 417 m/s

6. A time-delay relay that uses an RC timing circuit is called a(n)_________

  • solid-state, time-delay relay
  • adjustable relay
  • dashpot time-delay relay
  • motor-driven, time-delay relay

7. 1 Henry is equivalent to

  • Weber.Tesla
  • V.s/A
  • Tesla/s
  • Weber.A/s

8. Which of the following factors DOES NOT affect the self inductance of a coil?

  • The length of the coil
  • The current flows in the coil
  • The number of turn of the coil
  • The cross sectional area of the coil

9. A 10-turn ideal solenoid has an inductance of 4.0 mH. To generate an emf of 2.0 V the current should change at a rate of:

  • 0.5 A/s
  • 50 A/s
  • 250 A/s
  • 500 A/s

10. Which of the following has the largest inductance?

  • A solenoid of radius 3 cm, length 1 cm, and with 100 turns of wire per centimeter
  • A solenoid of radius 2 cm, length 2 cm, and with 100 turns of wire per centimeter
  • A solenoid of radius 1 cm, length 1 cm, and with 200 turns of wire per centimeter
  • A solenoid of radius 2 cm, length 5 cm, and with 100 turns of wire per centimeter

11. Which of the following is not the unit for magnetic field strength?

  • Tesla
  • Weber per meter squared
  • Weber per second squared
  • Gauss

12. Which of the following is not an example of an electromagnetic device?

  • Solenoid
  • Relay
  • Resistor
  • Motor

13. Determine the factors which will not increases the induce emf of a coil

  • increasing the magnetic field.
  • increasing the cross sectional area of the coil
  • increasing the number of turns of the coil
  • decreasing the strength of magnetic field

14. In order to induce a voltage across a coil ____.

  • The coil must be in motion
  • Current must be increasing
  • There must be relative motion between the coil and the magnetic field
  • The coil must be cut by at least 10^8 lines of force per second

15. Lenz's law states that the induced voltage across an inductor ____.

  • Always opposes the current through the inductor
  • Always opposes any change in current
  • Changes polarity as current changes direction
  • Always opposes the applied votage

16. The voltage induced across an inductor is inversely proportional to the rate of change of magnetic flux.

  • true
  • false

17. A 7.2 mH inductor is connected to a current source. What is the magnitude of the voltage in the inductor at time 𝑡 = 3.0 𝑠 if the current is 𝐼(𝑡) = 5.0 + 7.0𝑡 − 2.0𝑡^2?

  • 36 mV
  • 58 mV
  • 90 mV
  • 230 mV

18. A 5.6 mH inductor is connected to a current source.What is the magnitude of the voltage in the inductorat time 𝑡 = 4.0 𝑠 if the current is 𝐼(𝑡) = 10.0 + 9.0𝑡 −3.0𝑡^2?

  • 11 mV
  • 22 mV
  • 84 mV
  • 58 mV

19. What is the total voltage of six 1.5 V cells, connected in series?

  • 3 VDC
  • 6 VDC
  • 9 VDC
  • 12 VDC

20. The total inductance value of two inductors 10H and 15H of connected in series is…

  • 05 H
  • 10 H
  • 15 H
  • 25 H

21. In an electric DC power supply, a capacitor is commonly used to__________

  • block the current flow
  • increase the current flow
  • filter out the unwanted AC voltage
  • decrease the voltage

22. How power rating is specified for transformers?

  • Watts (W)
  • Voltage (V)
  • Volt ampere(VA)
  • Horse power(HP)

23. A coil that opposes any change in current flow is called a(n) __________

  • inductor
  • capacitor
  • transducer
  • oscillator

24. One of the effects a capacitor has in a DC circuit is that it will __________.

  • charge to a voltage equal to the source voltage
  • continue to charge until the source is completely drained
  • act like an open until it is fully charged
  • None of the above

25. The formula for calculating total parallel capacitance is __________

  • CT= C1 + C2 + C3...
  • (1/CT) = (1/C1) + (I/C2) + (1/C3)
  • CT= C1 * C2 * C3...
  • CT = C1 - C2 - C3 ....

26. A common inductor found in fluorescent light fixtures is a __________

  • starter
  • cathode
  • ballast
  • switcher

27. Which of the following is a type of capacitor?

  • Nonpolarized
  • Variable
  • All of the above
  • None of the above

28. The concept of a magnetic field being formed around a conductor when current flows through it is called __________.

  • capacitance
  • electromagnetism
  • flux
  • All of the above

29. Inductance is measured in __________.

  • Ohms
  • Farads
  • henrys
  • RPMs

30. __________ affects a DC circuit only when the current is first turned on, turned off, or when there is a charge in the load resistance.

  • capacitance
  • Inductance
  • A time delay
  • A relay

31. The resistance provided by an inductor in an AC circuit is called __________.

  • induced resistance
  • inductive reactance
  • electromotive force
  • All of the above

32. Which of the following is the correct formula for calculating total series inductance?

  • LT = L1 + L2 + L3...
  • LT = L1 * L2 * L3...
  • LT = (1/L1) + (1/L2) + (1/L3) ..
  • None of the above

33. Which of the following is the correct formula for calculating total parallel inductive reactance in a parallel circuit?

  • XLT = XL1 + XL2 + XL3 ...
  • XLT = XL1 * XL2 * XL3...
  • XLT = 1/[(1/XL1) + (1/XL2) + (1/XL3) ... ]
  • XLT = (1/XL1) + (1/XL2) + (1/XL3) ...

34. The energy stored by a capacitor is called a(n) __________.

  • induced voltage
  • electrostatic charge
  • voltage spike
  • All of the above

35. Capacitance is measured in __________.

  • Farads
  • henrys
  • Ohms
  • Volts

36. The trimmer capacitor is used for..

  • coupling
  • filtering
  • decoupling
  • fine tuning

37. Which value is equal to one picofarad?

  • 106 Farad
  • 1012 Farad
  • 10-6 Farad
  • 10-12 Farad

38. Which property of the capacitor stores electrical energy in electrostatic field?

  • Dielectric
  • Capacitance
  • Straycapacitance
  • Capacitivereactance

39. Which unit is used to measure capacitance value?

  • Mho
  • Ohm
  • Farad
  • Henry

40. What is the lowest voltage level of discharging the lead-acid battery?

  • 1.2 V
  • 1.5 V
  • 1.7 V
  • 1.85 V

41. What is the percentage of sulphuric acid in electrolyte used for lead-acid batteries?

  • 12%
  • 25%
  • 27%
  • 40%

42. Which energy is converted by the battery to produce electricity?

  • Electricalenergy into light energy
  • Chemical energyinto electrical energy
  • Mechanicalenergy into electrical energy
  • Electricalenergy into mechanical energy

43. A long narrow solenoid has length ℓ and a total of N turns, each of which has cross-sectional area A. Its inductance is:

  • μ0 N^2 Aℓ
  • μ0 N^2 A/ℓ
  • μ0 NA/ℓ
  • μ0 N^2 ℓ/A

44. How much energy is stored in a long solenoid with 660 turns, length 𝐿 = 3.2 𝑚, and cross sectional area 𝐴 = 121 𝑐𝑚^2, when the current in it is 𝐼 = 85 𝐴?

  • 1.10 𝑘𝐽
  • 9.1 1𝑘𝐽
  • 5.21 𝑘𝐽
  • 7.48 𝑘𝐽

45. How large a current must flow through a 1.2 H inductance so that the energy stored is 393 J?

  • 2.31 A
  • 25.6 A
  • 44.2 A
  • 107.1 A

46. Energy can be stored in many ways. What is theprimary energy storage form of an inductor?

  • Electric field
  • Magnetic field
  • Gravitational field
  • Spring displacement

47. A straight wire of length is oriented east-west and is in a magnetic field B pointing north. The wire is moving downward at a constant speed v. Which end of the rod is positively charged?

  • neither
  • the east end
  • the west end
  • both ends

48. A bar magnet is falling through a loop of wire with constant velocity. The south pole enters first. As the magnet leaves the wire, the induced current (as viewed from above) is:

  • clockwise.
  • counterclockwise.
  • zero.
  • along the length of the magnet.

49. According to Lenz’s law the direction of an induced current in a conductor will be that which tends to produce which of the following effects?

  • enhance the effect which produces it
  • produce a greater heating effect
  • produce the greatest voltage
  • oppose the effect which produces it

50. A metal rod is falling toward the surface of the Earth near the equator. As it falls, one end of the rod becomes positively charged due to the motional emf of the rod through the Earth's magnetic field. The rod is oriented so that:

  • the rod is vertical with the positive end higher.
  • the rod is horizontal with the positive end toward the north.
  • the rod is horizontal with the positive end toward the east.
  • the rod is horizontal with the positive end toward the west.

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