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1 | |
Like magnetic poles repel each other, whereas unlike magnetic poles attract each other. |
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| | A) | True |
| | B) | False |
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2 | |
Magnetic flux lines are drawn in such a way that the direction at any point is the same as the direction of the force exerted on a unit south pole placed at that point. |
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| | A) | True |
| | B) | False |
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3 | |
The weber is a unit of magnetic flux density. |
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| | A) | True |
| | B) | False |
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4 | |
An electron projected from right to left through a magnetic field directed into the page will be deflected downward. |
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| | A) | True |
| | B) | False |
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5 | |
The area of a hysteresis loop is a measure of flux density. |
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| | A) | True |
| | B) | False |
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6 | |
The right-hand rule can be used to determine the direction of a magnetic field surrounding a current-carrying conductor. |
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| | A) | True |
| | B) | False |
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7 | |
Two current-carrying conductors placed near each other will experience a force of attraction if their currents are oppositely directed. |
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| | A) | True |
| | B) | False |
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8 | |
The magnetic field lines for a solenoid are the same shape as those for a bar magnet. |
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| | A) | True |
| | B) | False |
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9 | |
A large hysteresis loop means a more efficient electromagnetic device. |
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| | A) | True |
| | B) | False |
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10 | |
Magnetic materials having a high permeability will generally have a low retentivity. |
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| | A) | True |
| | B) | False |
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11 | |
Which of the following is not a unit of magnetic induction of flux density? |
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| | A) | Weber per square meter |
| | B) | Gauss |
| | C) | Tesla |
| | D) | Weber |
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12 | |
Magnetic fields have no effect on |
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| | A) | electric charges at rest |
| | B) | electric charges in motion |
| | C) | permanent magnets at rest |
| | D) | permanent magnets in motion |
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13 | |
The magnetic flux density at a distance d from a long, current-carrying, straight wire is proportional to |
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| | A) | d |
| | B) | 1/d |
| | C) | d2 |
| | D) | 1/d2 |
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14 | |
Relative permeability is |
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| | A) | the ratio of flux density in a material to that for a vacuum |
| | B) | large for paramagnetic materials |
| | C) | small for ferromagnetic materials |
| | D) | equal to 4π x 10-7 T . m/A for a vacuum |
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15 | |
The current through a wire is directed into the page. If a magnetic field is directed from right to left, the force on the wire will be |
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| | A) | to the right |
| | B) | to the left |
| | C) | upward |
| | D) | downward |
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16 | |
An electron is projected from left to right into a flux density of 0.3 T directed into the paper. If the speed of the electron is 2 x 106 m/s, the magnetic force
will be |
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| | A) | 9.6 x 10-14 N |
| | B) | 6.9 x 10-14 N |
| | C) | 6.9 x 10-14 N |
| | D) | 4.8 x 10-14 N |
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17 | |
A proton (+1.6 x 10-19 C) is projected from left to right at a velocity of 2 x 106 m/s. If an upward force of 1 x 10-13 N is observed, the magnetic flux density perpendicular to the velocity is approximately |
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| | A) | 1.25 T out of the paper |
| | B) | 1.25 T into the paper |
| | C) | 0.31 T out of the paper |
| | D) | 0.31 T into the paper |
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18 | |
A rectangular loop of wire 20 cm wide and 30 cm long makes an angle of 40° with a magnetic flux density of 0.3 T. The flux penetrating the loop is approximately |
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| | A) | 0.01 Wb |
| | B) | 0.02 Wb |
| | C) | 2 Wb |
| | D) | 115 Wb |
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19 | |
The magnetic induction at a distance of 6 cm in air from a long, currentcarrying conductor is 12 x 10-6 T. The current in the wire is |
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| | A) | 1.8 A |
| | B) | 3.6 A |
| | C) | 4.8 A |
| | D) | 6.4 A |
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20 | |
A solenoid has 60 turns of wire and a length of 16 cm and supports a current of 10 A. The relative permeability of the core is 1200. The magnetic induction at the center is approximately |
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| | A) | 1.4 T |
| | B) | 2.83 T |
| | C) | 5.65 T |
| | D) | 11 T |
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21 | |
Hysteresis is the lagging of the behind the . |
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22 | |
According to the right-hand rule, if a current-carrying wire is grasped with the right hand so that the thumb points in the direction of the , the curled fingers of that hand point in the direction
of . |
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23 | |
A circular coil in the plane of the paper supports a clockwise electric current. The direction of the magnetic flux near the center is . |
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24 | |
The relative permeability of a material is the ratio of its to that for a(n) . |
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25 | |
refers to the condition under which all the magnetic domains in a material are aligned. |
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26 | |
The unit of flux density in the metric system of units is the , and the unit of magnetic flux is the . |
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27 | |
In applying the right-hand screw rule for magnetic effects on a conducting wire, the is turned into the . Then the direction of the will be the same as the direction of
advance of a right-hand screw. |
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28 | |
A magnetic field having a flux density of one tesla will exert a force of one on a charge of one moving perpendicular to the field with a velocity of one . |
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29 | |
Materials with a relative permeability slightly less than unit are said to be ; materials have permeabilities slightly greater than unity. |
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30 | |
The ability of some materials to retain magnetism after the magnetizing force has been removed is referred to as . |
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