MCQs in ELECTRICITY AND MAGNETISM
122. One oersted (Oe) is equivalent to ______ Gb/cm. A. 1 B. 10 C. 100 D. 1000
A. 1
128. A good conductor has how many valence electrons? A. 1 B. 4 C. 2 D. 8
A. 1
121. How much is the flux in Weber are there in a magnetic flux of 2000 lines A. 2 x 10^-5 B. 2 x 10^-3 C. 2 x 10^5 D. 2 x 10^3
A. 2 x 10^-5
99. Germanium atom has __ protons and __ electrons. A. 32, 32 B. 32, 42 C. 42, 32 D. 34, 34
A. 32, 32
141. How many electrons are needed in the valence orbit to give a material's stability? A. 8 B. 4 C. 6 D. 5
A. 8
1. What is the diameter of an atom? A. About 10^-10 m B. About 10^-10 cm C. About 10^-10 mm D. About 10^-10 µm
A. About 10^-10 m
64. The air space between poles of magnets A. Air gap B. Free space C. Vacuum D. Atmosphere
A. Air gap
105. A commercial alloy of aluminum nickel, and iron with cobalt, copper and titanium added to produce about 12 grades. A. Alnico B. Brass C. Aluminum D. Constantan
A. Alnico
92. The tiniest element of matter A. Atom B. Proton C. Electron D. Neutron
A. Atom
73. The magnetic field of a magnetized iron bar when strongly heated A. Becomes weaker B. Becomes stronger C. Reverses in direction D. is unchanged
A. Becomes weaker
52. Permeance is analogous to A. Conductance B. Reluctance C. Admittance D. Resistance
A. Conductance
127. Which of the following has the least number of valence electrons? A. Conductor B. Semiconductor C. Insulator D. Semi- insulator
A. Conductor
86. A magnetic material losses its ferromagnetic properties at a point called A. Curie temperature B. Inferred absolute temperature C. Room temperature D. Absolute temperature
A. Curie temperature
76. The emf produced in a wire by its motion across a magnetic field does not depend upon the A. Diameter of the wire B. Length of the wire C. Orientation of the wire D. Flux density of the field
A. Diameter of the wire
42. The process by which an emf and hence current is generated or induced in a conductor when there is a change in the magnetic flux linking the conductor is called A. Electromagnetic induction B. Mutual induction C. Faraday's law D. Electromagnetic interference
A. Electromagnetic induction
130. A negative ion results when an atom gains an additional A. Electron B. Proton C. Neutron D. Atom
A. Electron
124. An electron- volt (eV) is a unit of A. Energy B. Potential difference C. Charge D. Momentum
A. Energy
34. Lenz's law is the consequence of the law of conservation of A. Energy B. Charge C. Field lines D. Momentum
A. Energy
63. Refers to the non- metallic materials that have the ferromagnetic properties of iron. A. Ferrites B. Ferromagnetic C. Diamagnetic D. Paramagnetic
A. Ferrites
110. Which of the following electric quantities is vector in character? A. Field B. Charge C. Energy D. Potential Difference
A. Field
62. Refers to the magnetic lines A. Flux B. Hysteresis C. Current D. Magnetomotive force
A. Flux
115. What is the cgs unit of magnetomotive force? A. Gilbert B. Ampere- turn C. Maxwell D. Weber
A. Gilbert
18. Who discovered the most important electrical effects which is the magnetic effect? A. Hans Christian Oersted B. Sir Charles Wheatstone C. Georg Ohm D. James Clerk Maxwell
A. Hans Christian Oersted
31. Who discovered superconductivity in 1911? A. Kamerlingh Onnes B. Alex Muller C. Geory Bednorz D. Charles Coulomb
A. Kamerlingh Onnes
4. The net electrical charge in an isolated system remains constant. This is known as A. Law of conservation of charge B. Coulomb's first law C. Coulomb's second law D. Law of conservation of energy
A. Law of conservation of charge
80. Steel is hard to magnetize because of its A. Low permeability B. High permeability C. High density D. High retentivity
A. Low permeability
11. The space outside the magnet where its pole have a force of attraction or repulsion on a magnetic pole is called A. Magnetic field B. Electric field C. Electromagnetic field D. Free Space Field
A. Magnetic field
59. The force acting on a unit n- pole placed at that point is called A. Magnetic field intensity B. Electric field intensity C. Electromagnetic field intensity D. Intensity magnetization
A. Magnetic field intensity
47. The total number of magnetic lines of force in a magnetic field is called A. Magnetic flux B. Magnetic flux density C. Magnetic flux intensity D. Magnetic potential
A. Magnetic flux
33. The point in a magnet where the intensity of magnetic lines of force is maximum A. Magnetic pole B. South pole C. North pole D. Unit pole
A. Magnetic pole
5. The point in a magnet where the intensity of magnetic lines of force is maximum A. Magnetic pole B. South pole C. North pole D. Unit pole
A. Magnetic pole
8. The phenomenon by which a subtracts pieces of iron A. Magnetism B. Electromagnetism C. Naturalism D. Materialism
A. Magnetism
36. Who demonstrated the theory of electromagnetic induction in 1831? A. Michael Faraday B. Andre Ampere C. James Clerk Maxwell D. Charles Coulomb
A. Michael Faraday
37. Who discovered that a current-carrying conductor would move when placed in a magnetic field? A. Michael Faraday B. Andre Ampere C. Hans Christian Oersted D. Gustav Robert Kirchhoff
A. Michael Faraday
25. The magnetic potential in a magnetic circuit can be measured in terms of A. Mmf B. Emf C. Farad D. Coulomb
A. Mmf
107. The physical motion resulting from the forces of magnetic fields is called A. Motor action B. Rotation C. Repulsion D. Torque action
A. Motor action
43. The emf induced in a coil due to the changing current of another neighboring coil is called A. Mutually induced emf B. Self induced emf C. Statically induced emf D. Dynamically induced emf
A. Mutually induced emf
75. A current if flowing east along a power line. If the earth's field is neglected, the direction of the magnetic field below it is A. North B. South C. East D. West
A. North
13. Materials whose permeabilities are slightly greater than that of free space A. Paramagnetic B. Non- magnetic C. Ferromagnetic D. Diamagnetic
A. Paramagnetic
103. An alloy of 22 percent iron and 78 per cent nickel. A. Permalloy B. Alnico C. Constantan D. Manganin
A. Permalloy
150. One of the common application of an air- cored choke. A. Radio frequency B. Audio frequency C. Power supply D. Power transformer
A. Radio frequency
51. The ratio of the permeability of material to the permeability of air or vacuum. A. Relative permeability B. Relative permittivity C. Relative conductivity D. Relative reluctivity
A. Relative permeability
53. The property of magnetic materials of retaining magnetism after withdrawal of the magnetizing force is known as A. Retentivity B. Reluctivity C. Resistivity D. Conductivity
A. Retentivity
21. Which of the following magnetic materials can be easily magnetized in both direction? A. Soft magnetic materials B. Hard magnetic materials C. High hysteresis loss materials D. Low hysteresis loss materials
A. Soft magnetic materials
44. When a conductor is stationary and the magnetic field is moving or changing the emf induced is called A. Statically induced emf B. Mutually induced emf C. Self induced emf D. Dynamically induced emf
A. Statically induced emf
117. Flux density is measured in A. Tesla B. Weber C. Ampere- turn D. Maxwell
A. Tesla
84. Permeability means A. The conductivity of the material for magnetic lines of force B. The magnetization test in the material after exciting field has been removed C. The strength of an electromagnet D. The strength of the permanent magnet
A. The conductivity of the material for magnetic lines of force
146. The permeability of permalloy is A. Very much greater than permeability of air B. Slightly greater than permeability of air C. Slightly less than permeability of air D. Equal to the permeability of air
A. Very much greater than permeability of air
111. The quantity 10^6 Maxwell's is equivalent to one A. Weber B. Gauss C. Gilbert D. Tesla
A. Weber
77. The induced emf in a wire loop that is moved parallel to a uniform magnetic field is A. Zero B. Dependent on the area of the loop C. Dependent on the shape of the loop D. Dependent on the magnitude of the field
A. Zero
136. Electron is a Greek word for A. amber B. Fire C. Stone D. Heat
A. amber
68. All magnetic field originates from A. moving electric charge B. Iron atoms C. Magnetic domain D. Permanent magnets
A. moving electric charge
119. One ampere- turn is equivalent to __________ gilberts. A. 1.16 B. 1.26 C. 1.36 D. 1.46
B. 1.26
78. When a wire loop is rotated in a magnetic field the direction of the induced emf changes one in every _______ revolution A. 1/3 B. 1/2 C. 1/4 D. 2/3
B. 1/2
98. The K shell or the first shell has how many permissible number of orbiting electrons? A. 1 B. 2 C. 3 D. 4
B. 2
120. The magnetic flux of 2000 lines is how many Maxwells? A. 1000 B. 2000 C. 4000 D. 8000
B. 2000
100. A germanium atom has an atomic weight of 72. How many neutrons are there? A. 32 B. 40 C. 34 D. 36
B. 40
133. Hydrogen is an example of a ________ material. A. Paramagnetic B. Diamagnetic C. Ferromagnetic D. Non- magnetic
B. Diamagnetic
88. The emission of electrons from hot bodies is called A. Radiation effect B. Edison effect C. Skin effect D. Half effect
B. Edison effect
46. The branch of Engineering which deals with the magnetic effect of electric current is known as A. Magnetism B. Electromagnetism C. Electrical engineering D. Electronics engineering
B. Electromagnetism
138. What principle states that each electron in an atom must have a different set of quantum numbers? A. Inclusion principle B. Exclusion principle C. Quantum principle D. Electron principle
B. Exclusion principle
2. The magnitude of the induced emf in a coil is directly proportional to the rate of change of flux linkages. This is known as A. Joule's Law B. Faraday's second law of electromagnetic induction C. Faraday's first law of electromagnetic induction D. Coulomb's Law
B. Faraday's second law of electromagnetic induction
48. The current of electric circuit is analogous to which quantity of a magnetic circuit A. Mmf B. Flux C. Flux density D. Reluctivity
B. Flux
71. When the ferromagnetic substance is inserted in a current- carrying solenoid, the magnetic field is A. Greatly decreased B. Greatly increased C. Slightly decreased D. Slightly increased
B. Greatly increased
14. Who discovered the relationship between magnetism and electricity that serves as the foundation for the theory of electromagnetism? A. Luigi Galvani B. Hans Christian Oersted C. Andre Ampere D. Charles Coulomb
B. Hans Christian Oersted
7. If the solenoid is gripped by the right hand with the fingers pointing the direction of current flow, the outstretched thumb will then point the north pole. This is known as A. Right hand rule B. Helix rule C. End rule D. Cork screw rule
B. Helix rule
94. The simplest type of atom to exist is the ____________ atom. A. Helium B. Hydrogen C. Boron D. Oxygen
B. Hydrogen
35. Defined as a closed path in which magnetic induction or flux flows A. Electric circuit B. Magnetic circuit C. Electronic circuit D. Electromagnetic circuit
B. Magnetic circuit
109. Which of the following is a vector quantity? A. Magnetic potential B. Magnetic field intensity C. Magnetic permeability D. Flux density
B. Magnetic field intensity
65. One that has magnetic poles produced by internal atomic structure with no external current necessary A. Diamagnetic B. Permanent magnets C. Paramagnetic D. Electromagnetic
B. Permanent magnets
142. Residual magnetism refers to the flux density, which exists in the iron core when the magnetic field intensity is A. Minimized B. Reduced to zero C. Maximize D. Unity
B. Reduced to zero
30. The property of a material which opposes the creation of magnetic flux in it A. Resistance B. Reluctance C. Permeance D. Conductance
B. Reluctance
20. Referred to as the specific reluctance of a material A. Resistivity B. Reluctivity C. Conductivity D. Permeability
B. Reluctivity
140. Which of the following statements is TRUE? A. Silicon dioxide is a good B. The current carriers in conductors are valence electrons C. For conductors, the valence electron are strongly attracted to the nucleus D. The valence electrons are located in the nucleus of an atom
B. The current carriers in conductors are valence electrons
91. The contribution to the ionization in an ionization chamber by electrons liberated from the walls. A. Skin effect B. Walt effect C. Hall effect D. Edison effect
B. Walt effect
113. What is the SI unit of magnetic flux? A. Tesla B. Weber C. Maxwell D. Gauss
B. Weber
148. The force between two magnetic poles is ____________ their poles strength. A. equal to B. directly proportional to C. inversely proportional to D. directly proportional to the square root of
B. directly proportional to
70. The magnetic field inside a solenoid A. is zero B. is uniform C. increases with distance from the axis D. decreases with distance from the axis
B. is uniform
97. The diameter of a hydrogen atom is approximately ________cm. A. 1.1 x 10^-6 B. 1.1 x 10^-7 C. 1.1 x 10^-8 D. 1.1 x 10^-9
C. 1.1 x 10^-8
101. How many neutrons does a copper atom have? A. 32 B. 33 C. 34 D. 29
C. 34
114. What is the unit of magnetomotive force? A. Volt B. Tesla C. Ampere - turn D. Weber
C. Ampere - turn
23. A law establishing the fact that the algebraic sum of the rises and drops of the mmf around a closed loop of a magnetic circuit is equal to zero. A. Kirchhoff's circuital law B. Maxwell's circuital law C. Ampere's circuital law D. Coulomb's circuital law
C. Ampere's circuital law
112. What is the unit of reluctance? A. Maxwell B. Gauss C. At/Wb D. Weber
C. At/Wb
9. A law that states that the current in a thermionic diode varies directly with the three-halves power of anode voltage and inversely with the square of the distance between the electrodes, provided operating conditions are such that the current is limited only by the space charge. A. Hall's law B. Joule's law C. Child's law D. Coulomb's law
C. Child's law
55. The amount of magnetizing force to counter balance the residual magnetism of a magnetic material is referred to as A. Reluctivity B. Susceptivity C. Coercivity D. Retentivity
C. Coercivity
41. If the right handed bottle-opener cork screw is assumed to be along the conductor so as to advance in the direction of current flow, the motion of its handle will indicate the direction of magnetic flux produced around the conductor. This is known as A. Right hand rule B. Left hand rule C. Cork screw rule D. End rule
C. Cork screw rule
149. The magnetic energy stored in an inductor is ______ current. A. Directly proportional to B. Inversely proportional to C. Directly proportional to the square of D. Inversely proportional to the square of
C. Directly proportional to the square of
82. A group of magnetically aligned atoms is called A. Range B. Lattice C. Domain D. Crystal
C. Domain
95. What revolves about the positive nucleus in a definite orbit? A. Atom B. Proton C. Electron D. Neutron
C. Electron
28. Whenever a flux inking a coil or current changes, an emf is induced in it. This is known as A. Joule's LawC. Faraday's first law of electromagnetic induction B. Coulomb's Law C. Faraday's first law of electromagnetic induction D. Faraday's second law of electromagnetic induction
C. Faraday's first law of electromagnetic induction
38. Whenever a conductor cuts magnetic flux, an emf is induced in it. This is known as A. Coulomb's law B. Joule's law C. Faraday's law D. Ohm's law
C. Faraday's law
134. Cobalt is an example of a _______ material. A. Paramagnetic B. Diamagnetic C. Ferromagnetic D. Non- magnetic
C. Ferromagnetic
15. Materials that have very high permeabilities (hundreds and even thousands times of that of free space) A. Paramagnetic B. Non- magnetic C. Ferromagnetic D. Diamagnetic
C. Ferromagnetic
57. Defined as the number of lines per unit area through any substance in a plane at right angles to the lines of force A. Flux B. Flux lines C. Flux density D. Flux intensity
C. Flux density
87. Small voltages generated by a conductor with current in an external magnetic field. A. Skin effect B. Magnetic effect C. Hall effect D. Flywheel Effect
C. Hall effect
90. An effect which is generally used in the gausameter to measure flux density. A. Skin effect B. Magnetic effect C. Hall effect D. Flywheel effect
C. Hall effect
104. An alloy of 40 percent iron and 60 percent nickel. A. Alnico B. Permalloy C. Hipernik D. Manganin
C. Hipernik
61. The lagging effect between flux density of the material and the magnetizing force applied A. Permeance B. Eddy current C. Hysteresis D. Reluctance
C. Hysteresis
131. An atom or a group of atoms that carries a net electric charge. A. Positive ion B. Negative ion C. Ion D. Electron
C. Ion
10. Who developed the electromagnetic theory of light in 1862? A. Heinrich Rudolf Hertz B. Wilhelm Rontgen C. James Clerk Maxwell D. Andre Ampere;
C. James Clerk Maxwell
67. Used to maintain strength of magnetic field A. Container B. Air gap C. Keeper D. Source
C. Keeper
45. Which of the following is a natural magnet? A. Steel B. Magnesia C. Lodestone D. Soft iron
C. Lodestone
32. A substance that attracts pieces iron A. Conductor B. Semiconductor C. Magnet D. All of the above
C. Magnet
17. The straight line passing through the two poles of magnet is called A. Real axis B. Cartesian axis C. Magnetic axis D. Imaginary axis
C. Magnetic axis
24. The phenomenon by which a magnetic substance becomes a magnet when it is place near a magnet A. Magnetic effect B. Magnetic phenomenon C. Magnetic induction D. Electromagnetic induction
C. Magnetic induction
60. The ratio between the intensity of magnetization produced in a substance to the magnetizing force producing it A. Magnetic Reluctivity B. Magnetic Resistivity C. Magnetic susceptibility D. Magnetic conductivity
C. Magnetic susceptibility
116. The unit of flux is _____________ in cgs system. A. Tesla B. Gilbert C. Maxwell D. Oersted
C. Maxwell
49. It is the reciprocal of reluctance and implies the case of readiness with which magnetic flux is developed. A. Resistance B. Conductance C. Permeance D. Inductance
C. Permeance
139. The energy stored in an electrostatic field or electromagnetic field is called A. Electromagnetic energy B. Kinetic energy C. Potential energy D. Rest energy
C. Potential energy
54. The quantity of magnetism retained by a magnetic material after withdrawal of the magnetizing force is called A. Leftover magnetism B. Hysteresis C. Residual magnetism D. Coercivity
C. Residual magnetism
129. Which element has four valence electrons? A. Conductor B. Insulator C. Semiconductor D. Semi- insulator
C. Semiconductor
106. The idea of preventing one component from affecting another through their common electric and magnetic field is referred to as A. Hall effect B. Grounding C. Shielding D. Limiting
C. Shielding
81. Paramagnetic substance has a relative permeability of A. Slightly less than one B. Equal to one C. Slightly equal to one D. Very much greater than one
C. Slightly equal to one
66. Magnetic effects of the earth as a huge magnet with north and south poles. A. Diamagnetic B. Ferromagnetic C. Terrestrial magnetism D. Terrestrial ferromagnetism
C. Terrestrial magnetism
79. The magnetic flux through a wire loop in a magnetic field does not depend on A. The area of the loop B. The magnitude of the field C. The shape of the loop D. The angle between the plane of the loop and the direction
C. The shape of the loop
135. The evaporation of electrons from a heated surface is called A. Radiation B. Convection C. Thermionic emission D. Conduction
C. Thermionic emission
85. _________ is an electromagnet with its core in the form of a close magnetic ring. A. Solenoid B. Paraboloid C. Toroid D. Cycloid
C. Toroid
19. Define as that pole which when placed in air from a similar and equal pole repels it with a force of newtons A. North pole B. South pole C. Unit pole D. Magnetic pole
C. Unit pole
89. The ability of a mechanically stressed ferromagnetic wire to recognize rapid switching of magnetization when subjected to a dc magnetic field. A. Wartheim effect B. Wiedemann effect C. Wiegand effect D. Edison effect
C. Wiegand effect
118. The customary energy unit in atomic and nuclear physics is A. Joule B. Volt- coulomb C. electron-volt D. Walt- second
C. electron-volt
123. One electron volt (1 eV) is equivalent to ____ joules A. 1.3 x 10^-19 B. 1.4 x 10^-19 C. 1.5 x 10^-19 D. 1.6 x 10^-19
D. 1.6 x 10^-19
125. The unit of electrical energy is A. Joule B. Watt- second C. Kilowatt- hour D. All of these
D. All of these
27. Lenz' law states that the direction of the induced emf and hence current A. Is determined by the rate of current flux B. Is found by the right hand rule C. Is found by the left hand rule D. Always opposes the cause producing it
D. Always opposes the cause producing it
26. Who demonstrated that there are magnetic effects around every current-carrying conductor and that current-carrying conductors can attract and repel each other just like magnets? A. Luigi Galvani B. Hans Christian Oersted C. Charles Coulomb D. Andre Ampere
D. Andre Ampere
93. All matters (gas, liquid and solid) are composed of A. Neutrons B. Particles C. Electrons D. Atoms
D. Atoms
3. The force of attraction or repulsion between two magnetic poles is inversely proportional to the square of the distance between them. This is known as A. Newton's first law B. Faraday's first law of electromagnetic induction C. Coulomb's first law D. Coulomb's second law
D. Coulomb's second law
29. Which of the following materials has permeability slightly less than that of free space? A. Paramagnetic B. Non- magnetic C. Ferromagnetic D. Diamagnetic
D. Diamagnetic
16. If on looking at any one end of a solenoid; the direction of current flow is found to be clockwise then the end under observation is a south pole. This is known as A. Right hand rule B. Left hand rule C. Cork screw rule D. End Rule
D. End Rule
108. Flux linkages equals A. Flux times area of core B. Flux times number of turns times area of core C. Flux times number of turns times length of core D. Flux times number of turns
D. Flux times number of turns
144. The core of a magnetic equipment uses a magnetic material with A. Least permeability B. Low permeability C. Moderate permeability D. High permeability
D. High permeability
58. Defined as the flux density produced in it due to its own induced magnetism A. Magnetic field intensity B. Electric field intensity C. Electromagnetic field intensity D. Intensity magnetization
D. Intensity magnetization
83. The force between two magnetic poles varies with the distance between them. The variation is _________ to the square of that distance. A. Equal B. Greater than C. Directly proportional D. Inversely proportional
D. Inversely proportional
132. Hysteresis refers to the _______________ between flux density of the material and the magnetizing force applied. A. Leading effect B. Ratio C. Equality D. Lagging effect
D. Lagging effect
56. The ratio of the total flux (flux in iron path) to the useful flux (flux in air gap) A. Leakage flux B. Leakage current C. Leakage coefficient D. Leakage factor
D. Leakage factor
39. A law that states that the polarity of the induced voltage will oppose the change in magnetic flux causing the induction. A. Joule's law B. Faraday's law C. Coulomb's law D. Lenz' law
D. Lenz' law
147. A t/m is a unit of A. Mmf B. Emf C. Reluctance D. Magnetizing force
D. Magnetizing force
22. The force which set ups or tends to set up magnetic flux in a magnetic circuit A. Dynamic force B. Electromotive force C. Potential difference D. Magnetomotive force
D. Magnetomotive force
102. Bonding of atoms that is due to the force of attraction between positive ions and a group of negative ions A. Ionic bond B. Covalent Bond C. Electrostatic Bond D. Metallic bond
D. Metallic bond
96. The uncharged particles which have no effect on its atomic charge. A. Nucleons B. Electrons C. Protons D. Neutrons
D. Neutrons
145. Which of the following is a paramagnetic material? A. Carbon B. Copper C. Bismuth D. Oxygen
D. Oxygen
50. The ability of a material to conduct magnetic flux through it. A. Permittivity B. Reluctivity C. Conductivity D. Permeability
D. Permeability
137. Gases whose particles are charged are known as A. Conductors B. Insulators C. Gaseous Conductors D. Plasma
D. Plasma
40. If you hold the conductor with right hand so that the stretched thumb points in the direction of the current, then encircling fingers will give the direction of magnetic lines of force round the conductor. This is known as A. Left hand cork screw rule B. Right hand cork screw rule C. Left hand rule D. Right hand rule
D. Right hand rule
6. The emf induced in a coil due to the change of its own flux linked with it is called A. Mutually induced emf B. Dynamically induced emf C. Statically induced emf D. Self induced emf
D. Self induced emf
69. Magnetic fields do not interact with A. Moving permanent magnets B. Stationary permanent magnets C. Moving electric charges D. Stationary electric charges
D. Stationary electric charges
126. Electrons at the outer shell are called A. Outer shell electrons B. Inner shell electrons C. Semiconductor electrons D. Valence electrons
D. Valence electrons
143. Magnetic intensity is a A. Phasor quantity B. Physical quantity C. Scalar quantity D. Vector quantity
D. Vector quantity
12. States that the ratio of the thermal conductivity is proportional to the absolute temperature for all metals. A. Wien's displacement law B. Hartleys law C. Hall's law D. Wiedemann Franz law
D. Wiedemann Franz law
72. The magnetic field of a bar magnet most closely resembles the magnetic field of A. a horseshoe magnet B. a straight current- carrying wire C. a stream of electrons moving parallel to one another D. a current- carrying wire loop
D. a current- carrying wire loop
74. A permanent magnet does not exert a force on A. an unmagnetized iron bar B. a magnetized iron bar C. a moving electric charge D. a stationary electric charge
D. a stationary electric charge