Electromagnetism and DC Motor
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Questions and Answers

What is the unit of magnetic flux?

  • Wb/m
  • Weber (correct)
  • Tesla
  • Henry

What is the purpose of the commutator in a DC motor?

  • To produce a rotating magnetic field
  • To supply electrical current to the armature winding (correct)
  • To convert mechanical energy into electrical energy
  • To convert electrical energy into mechanical energy

What is the term for the direction of force in a DC motor?

  • Lenz's law
  • Fleming's right hand rule
  • Fleming's left hand rule (correct)
  • Faraday's law

What is the function of the stator in a DC motor?

<p>To produce a stationary magnetic field (C)</p> Signup and view all the answers

What is the term for the magnetic field strength?

<p>Magnetic field strength (B)</p> Signup and view all the answers

What is the effect of increasing the number of turns around a core and/or increasing the current through the coil on the magnetic field strength?

<p>The magnetic field strength increases. (A)</p> Signup and view all the answers

What is the unit of measurement for the magnetomotive force (mmf)?

<p>Ampere-turns (At) (B)</p> Signup and view all the answers

What is the permeability of nonmagnetic materials, such as copper, aluminum, wood, glass, and air, compared to that of free space?

<p>Same as that of free space (C)</p> Signup and view all the answers

What is the relationship between the magnetic field strength and the type of core used in an electromagnet?

<p>The magnetic field strength is affected by the permeability of the core material. (D)</p> Signup and view all the answers

What is the analogy between magnetic circuits and electric circuits?

<p>Magnetomotive force is analogous to applied voltage. (B)</p> Signup and view all the answers

What is the purpose of placing certain materials, such as iron, steel, or cobalt, within a coil?

<p>To increase the magnetic field strength. (C)</p> Signup and view all the answers

What is the primary factor that determines the strength of a magnetic field in a particular region?

<p>The density of flux lines in that region (C)</p> Signup and view all the answers

What happens when unlike poles of two permanent magnets are brought together?

<p>The magnets attract and the flux distribution is strengthened (C)</p> Signup and view all the answers

How can the direction of the magnetic flux lines be determined?

<p>By placing the thumb of the right hand in the direction of conventional current flow and noting the direction of the fingers (B)</p> Signup and view all the answers

What is the characteristic of a magnetic field around a permanent magnet?

<p>It is represented by magnetic flux lines (B)</p> Signup and view all the answers

What is the relationship between the magnetic field strength and the density of flux lines in a particular region?

<p>The magnetic field strength is directly proportional to the density of flux lines (B)</p> Signup and view all the answers

What is the result of bringing like poles of two permanent magnets together?

<p>The magnets repel and the flux distribution is disrupted (A)</p> Signup and view all the answers

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