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Magnetism And Electromagnetism Online Exam Quiz

Important questions about Magnetism And Electromagnetism. Magnetism And Electromagnetism MCQ questions with answers. Magnetism And Electromagnetism exam questions and answers for students and interviews.

1. What is the flux density in a magnetic field in which the flux in 0.1 m 2 is 600 µWb?

Options

A : 6,000 µT

B : 600 µT

C : 600 T

D : 6 T

2. The induced voltage across a coil with 250 turns that is located in a magnetic field that is changing at a rate of 8 Wb/s is

Options

A : 1,000 V

B : 2,000 V

C : 31.25 V

D : 3,125 V

3. The unit for reluctance is

Options

A : tesla

B : At/Wb

C : At/m

D : Wb

4. If a loop in a basic dc generator suddenly begins rotating at a faster speed, the induced voltage

Options

A : remains unchanged

B : reverses polarity

C : increases

D : decreases

5. When the current through the coil of an electromagnet reverses, the

Options

A : direction of the magnetic field reverses

B : direction of the magnetic field remains unchanged

C : magnetic field expands

D : magnetic field collapses

6. What is the reluctance of a material that has a length of 0.07 m, a cross-sectional area of 0.014 m 2 , and a permeability of 4,500 µWb/At × m?

Options

A : 1111 At/Wb

B : 111 At/Wb

C : 11 At/Wb

D : 1 At/Wb

7. When a solenoid is activated, the force that moves the plunger is

Options

A : an electromagnetic field

B : a permanent magnetic field

C : varying voltage

D : a steady current

8. There is 900 mA of current through a wire with 40 turns. What is the reluctance of the circuit if the flux is 400 µWb?

Options

A : 14,400 At/Wb

B : 1,440 At/Wb

C : 9,000 At/Wb

D : 90,000 At/Wb

9. The voltage induced across a certain coil is 200 mV. A 120 ? resistor is connected to the coil terminals. The induced current is

Options

A : 1.7 mA

B : 16 mA

C : 12 mA

D : 120 mA

10. An electromagnetic field exists only when there is

Options

A : an increasing current

B : decreasing current

C : voltage

D : current

1. A coil of wire is placed in a changing magnetic field. If the number of turns in the coil is decreased, the voltage induced across the coil will

Options

A : increase

B : decrease

C : remain constant

D : be excessive

2. A basic one-loop dc generator is rotated at 90 rev/s. How many times each second does the dc output voltage peak (reach maximum)?

Options

A : 90

B : 180

C : 270

D : 360

3. What is the flux density when the flux is 5.5 µWb and the cross-sectional area is 6 × 10 ?3 m 2 ?

Options

A : 91.7 µT

B : 917 µT

C : 91 T

D : 9.7 T

4. If the steel disk in a crankshaft position sensor has stopped with the tab in the magnet's air gap, the induced voltage

Options

A : increases

B : decreases

C : is zero

D : will remain constant

5. A relay is an electromagnetically controlled mechanical device in which electrical contacts are opened or closed by a magnetizing current.

Options

A : True

B : False

C :

D :

6. If a conductor is moved back and forth at a constant rate in a constant magnetic field, the voltage in the conductor will reverse polarity.

Options

A : True

B : False

C :

D :

7. Ampere-turn is the unit of magnetomotive force (mmf).

Options

A : True

B : False

C :

D :

8. The tesla is the unit of magnetic flux.

Options

A : True

B : False

C :

D :

9. Materials with a low retentivity do not retain a magnetic field very well.

Options

A : True

B : False

C :

D :

10. Hysteresis is the number of lines of force per unit area in a magnetic field.

Options

A : True

B : False

C :

D :

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