A: 0.25
B: 0.50
C: 1
D: 2
E: 4
举一反三
- 1) What happens to the magnitude of the magnetic field inside a long solenoid if the current is doubled? A: It becomes four times larger. B: It becomes twice as large. C: It is unchanged. D: It becomes one-half as large. E: It becomes one-fourth as large.
- When the medium is magnetized, the molecular magnetic moment inside the paramagnetic material turns to the opposite direction of the external magnetic field
- There is no magnetic field in an ideal conductor, but there is a magnetic field inside because of the surface current。
- 5) Which one of the glowing magnetic field gives the largest magnitude? A: the field 2 cm away from a long, straight wire carrying a current of 3 A B: the field at the center of a flat, compact, circular coil, 2 cm in radius, with 10 turns, carrying a current of 0.3 A C: the field at the center of a solenoid 2 cm in radius and 200 cm long, with 1000 turns, carrying a current of 0.3A D: the field at the center of a long, straight, metal bar, 2 cm in radius, carrying a current of 300 A E: a field of 1 mT
- The<br/>magnetic field lines are used to visually describe the distribution<br/>of the magnetic field around the magnet. For the following<br/>statement,( <br/>) is wrong. A: Each<br/>magnetic field line is a closed loop curve B: No<br/>two magnetic field lines can cross each other C: The<br/>length of the magnetic field line reflects the strength of the<br/>magnetic field D: The<br/>tangential direction of any point on any of the magnetic lines is the<br/>direction of the magnetic field at that point
内容
- 0
The curl equation [img=154x44]1803a2a153c85f5.png[/img]shows that : A: The time-varying magnetic field can generate an electric field, in which the elecric field lines is closed around the magnetic field line. B: The time-varying magnetic field can generate a magneitc field, in which the magnetic field lines is closed around the electric field line. C: The magnetic field lines is closed themselves. D: Flux continuity
- 1
4）磁共振成像系统不包括( ) A: static magnetic field B: RF pulse system C: gradient magnetic field D: filtration
- 2
Which statement as follows is right? A: The potential equals everywhere the magnitude of electric field intensity is equal. B: The magnitude of electric field intensity equals everywhere the potential is equal. C: The potential must be high where the magnitude of electric field intensity is great. D: The potential is not necessarily zero where the magnitude of electric field equals zero.
- 3
When the external magnetic field is removed, most or all of the magnetism of soft magnetic materials will not be lost, and the coercivity is very large.
- 4
If the magnetic field B through<br/>a loop of wire is increasing, the<br/>induced magnetic field will be A: in<br/>the same direction as B B: in<br/>the opposite direction as B C: perpendicular<br/>to B D: at<br/>an acute angle to B E: there<br/>is no induced magnetic field