問題一覧
1
discovered in Magnesia (West Turkey)
- difficult to detect and measure
- exists when there is a charged particle in motion
Magnetism
2
oxide of iron
Magnetite
3
rodlike stone that when suspended by a string would rotate back and forth
Lodestone
4
of a charged particle is perpendicular to its motion
- also created when electric current/electrons is conducted through the wire
- its intensity is proportional to the electric current
- intensity is greatly increased by an iron core
- Any charge in motion induces this
Magnetic field
5
motion of electrons rotating in a clockwise or counterclockwise axis
- creates a magnetic field which is neutralized in electron pairs
Electron spin
6
lines of a magnetic field
Closed loops
7
Atoms with this number of electrons in any shell exhibit a very small magnetic field
Odd number
8
created by protons spinning on its axis that creates a magnetic dipole, basis for MRI
Magnetic moment
9
The accumulation of many atomic magnets with their dipoles aligned
Magnetic Domain
10
When all magnetic domains in an object are aligned, it acts like a what?
Magnet
11
in its normal state, magnetic domains are distributed in what way?
Randomly distributed
12
ability of a material to attract the lines of magnetic field intensity
Magnetic permeability
13
When an external force acts on the magnetic domains, randomly oriented dipoles do what with the magnetic field?
Align
14
good example of a natural magnet
Earth
15
2 Types of Naturally Occurring Magnets
* Earth - has a magnetic field because it spins on its axis * Lodestones - exhibit strong magnetism presumably because they have remained undisturbed
16
Types of Artificially induced permanent magnets
* bar, horse-shaped made out of iron * Compass * Destroyed by: heating, hitting with hammer
17
* Consist of wire wrapped around an iron core
* current-carrying coil of wire wrapped around an iron core which intensifies the induced magnetic field
Electromagnets
18
magnetic state that cannot be artificially magnetized
Diamagnetic
19
magnetic state that can be magnetized by exposure to a magnetic field.
Ferromagnetic
20
magnetic state that is slightly attracted to magnet and loosely influenced by an external magnetic field. Contrast agents used in MRI.
Paramagnetic
21
magnetic state unaffected by magnetic field
Nonmagnetic
22
degree to which a material can be magnetized is called this
Magnetic susceptibility
23
the ends of a magnet and are in pairs; the north and south pole.the ends of a magnet and are in pairs; the north and south pole.
Magnetic Poles
24
will create a magnetic field along its axis of spin.
Spinning charged particles
25
will create a magnetic field perpendicular to that particles motion.
Moving charged particle
26
some materials such as ferromagnetic materials can be made magnetic by this
Induction
27
imaginary lines of the magnetic field and its density is proportional to the intensity of the magnetic field
Magnetic lines of induction
28
who said this
- Set out to show that electricity and magnetism are related.
- Moving or spinning electric charges should induce a magnetic field.
- Used an electric circuit and a compass to prove his experiment.
Hans Christian Oersted
29
who said this
* 1st law of magnetic induction
* An electric current is created in a circuit if some part of that circuit is in a changing magnetic field.
* His experiments shows that magnetic fields can create electric currents
* He showed the lines of a magnetic field by sprinkling iron filings on a piece of paper covering a magnet.
Michael Faraday (Faraday’s Law)
30
who said this?
* 2nd law of magnetic induction
* An induced current within a conductive coil produces a magnetic field to oppose the change in magnetic field which produced it
Lenz’s Law (Heinrich Friedrich Emil Lenz)
31
Who said this?
* Proposed that if a changing magnetic field can induce an electric field, then a changing electric field should induce a magnetic field
* Changing fields should move at a speed equal to the speed of light.
* The magnetic force is proportional to the product of the magnetic pole strengths divided by the square of the distance between them.
James Clerk Maxwell
32
Sl unit of magnetic field strength
Tesla
33
conventional unit of magnetic field strength
Gauss
34
magnet used in an MRI system
3 Tesla
35
1 Tesla is equivalent to?
10,000 Gauss
36
The Earth's magnetic field is approximately what at the equator
50 uT
37
The Earth's magnetic field is approximately what at the poles
100uT
38
Electricity and Magnetism were viewed as separate effects until the?
19th Century
39
observed that a dissected frog leg twitched when touched by two different metals as if it had been touched by two different metals (late 1700s).
Luigi Galvani
40
who said this
- questioned whether an electric current might be produced when two different metals are made into contact.
- He succeeded in producing a feeble electric current using zinc and copper plates.
- stacked the copper-zinc plates to form a Voltaic pile to increase the current.
Alessandro Volta
41
each zinc copper pile
Cell of a battery
42
what is
precursor to the modern battery
- paved the way to the creation of modern batteries which is an example of sources of electric potential.
Voltaic pile
43
modern dry cells use this as the positive electrode surrounded by an electrolytic paste housed in a negative zinc cylindrical can.
Carbon rods
44
electric potential is measured in units of joule per coulomb
Volts
45
The magnetic field produced by an electromagnet is the same as that produced by a bar of magnet
True
46
* An electric current is induced in a circuit if some part of that circuit is in a changing magnetic field.
* No physical motion is needed.
* If the current is increased in the electromagnet, the magnetic field will also change and induce a current in the coil
Electromagnetic Induction
47
What law states that the magnitude of the induced current depends on 4 factors:
* Strength and the Velocity of the magnetic field as it moves past the conductor
* The angle of the conductor in the magnetic field
* Number of turns in the conductor
Faraday’s law
48
What motor possesses this
* An electric current produces a mechanical motion.
* Motion of the compass needle.
* Has the same components as an electric generator.
* Electric energy is supplied to the current loop to produce motion.
* Uses many turns of wire for the current loop and many bars of magnets to create an external magnetic field
Electric Motors
49
what motor is this
* Mechanical motion induces electricity in a coil of wire.
* The motion of a magnet near a coil of wire.
* A coil of wire is places in a strong magnetic field between two magnetic poles.
* The coil is rotated by mechanical energy which in turn induces an electric current.
* The net effect of an electric generator is to convert mechanical energy into electrical energy.
Electric Generators
50
What motor is this
* The type of motor used in x-ray tubes.
* The rotating rotor is a shaft made of bars of copper and soft iron fabricated into one mass.
* The external magnetic field is supplied by several fixed electromagnets called Stators.
* Powers the rotating anode of an x-ray tube.
Induction Motor
51
devices that uses the interacting magnetic fields produced by changing electric currents
- does not convert but transforms electric potential and current into higher or lower intensity.
- Operates in alternating current.
- Has a primary turns of wire and a secondary turns of wire
Transformers
52
where input of electricity happens
Primary side
53
where output of electricity happens
Secondary side
54
If primary side has less turns of wire than the secondary side, the result will be this
Higher Voltage & Lower Current
55
the change in voltage is directly proportional to the ratio of the number of turns (windings) of the secondary coil (Ns) to the number of turns in the primary coil (Np)
Transformer Law (Voltage)
56
as the voltage changes across a transformer, the current changes also.
Transformer Law (Current)
57
Transformer that is
* Built about a square core of ferromagnetic material.
* The ferromagnetic core is not a single piece, but built up of laminated layers of iron.
* Helps reduce energy losses, resulting to greater efficiency.
Closed core transformer
58
transformer that
* Consist of an iron core with only one winding of wire about it.
* The single winding acts as the primary and secondary winding.
* Connections are made at different points on the coil for both the primary and secondary sides.
* Varies both voltage and current.
* Generally smaller and its use is restricted to cases in which a small step up or step down in voltage is required.
* Not suitable for x-ray imaging.
Autotransformer
59
* Confines even more of the magnetic field lines of the primary winding because the secondary winding is wrapped around it and there are essentially two closed cores.
* More efficient than closed-core transformer.
* Most currently used transformer
Shell type transformer
60
Does not use a ferromagnetic core to link the primary and secondary coils.
Air-core transformer
61
Primary and Secondary coils are wound on one cylinder. Magnetic path is partially through the core and partially through the surrounding air
Open-core transformer
62
* A current that opposes the magnetic field that induced it creating a loss of transformer efficiency.
* Closed-core transformer reduces this
Eddy Current
63
an additional resistance by alternate reversal of the magnetic field caused by alternating current.
Hysteresis Loss
64
* Electric current in the copper wire experience resistance.
* Results in heat generation.
Resistance
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問題一覧
1
discovered in Magnesia (West Turkey)
- difficult to detect and measure
- exists when there is a charged particle in motion
Magnetism
2
oxide of iron
Magnetite
3
rodlike stone that when suspended by a string would rotate back and forth
Lodestone
4
of a charged particle is perpendicular to its motion
- also created when electric current/electrons is conducted through the wire
- its intensity is proportional to the electric current
- intensity is greatly increased by an iron core
- Any charge in motion induces this
Magnetic field
5
motion of electrons rotating in a clockwise or counterclockwise axis
- creates a magnetic field which is neutralized in electron pairs
Electron spin
6
lines of a magnetic field
Closed loops
7
Atoms with this number of electrons in any shell exhibit a very small magnetic field
Odd number
8
created by protons spinning on its axis that creates a magnetic dipole, basis for MRI
Magnetic moment
9
The accumulation of many atomic magnets with their dipoles aligned
Magnetic Domain
10
When all magnetic domains in an object are aligned, it acts like a what?
Magnet
11
in its normal state, magnetic domains are distributed in what way?
Randomly distributed
12
ability of a material to attract the lines of magnetic field intensity
Magnetic permeability
13
When an external force acts on the magnetic domains, randomly oriented dipoles do what with the magnetic field?
Align
14
good example of a natural magnet
Earth
15
2 Types of Naturally Occurring Magnets
* Earth - has a magnetic field because it spins on its axis * Lodestones - exhibit strong magnetism presumably because they have remained undisturbed
16
Types of Artificially induced permanent magnets
* bar, horse-shaped made out of iron * Compass * Destroyed by: heating, hitting with hammer
17
* Consist of wire wrapped around an iron core
* current-carrying coil of wire wrapped around an iron core which intensifies the induced magnetic field
Electromagnets
18
magnetic state that cannot be artificially magnetized
Diamagnetic
19
magnetic state that can be magnetized by exposure to a magnetic field.
Ferromagnetic
20
magnetic state that is slightly attracted to magnet and loosely influenced by an external magnetic field. Contrast agents used in MRI.
Paramagnetic
21
magnetic state unaffected by magnetic field
Nonmagnetic
22
degree to which a material can be magnetized is called this
Magnetic susceptibility
23
the ends of a magnet and are in pairs; the north and south pole.the ends of a magnet and are in pairs; the north and south pole.
Magnetic Poles
24
will create a magnetic field along its axis of spin.
Spinning charged particles
25
will create a magnetic field perpendicular to that particles motion.
Moving charged particle
26
some materials such as ferromagnetic materials can be made magnetic by this
Induction
27
imaginary lines of the magnetic field and its density is proportional to the intensity of the magnetic field
Magnetic lines of induction
28
who said this
- Set out to show that electricity and magnetism are related.
- Moving or spinning electric charges should induce a magnetic field.
- Used an electric circuit and a compass to prove his experiment.
Hans Christian Oersted
29
who said this
* 1st law of magnetic induction
* An electric current is created in a circuit if some part of that circuit is in a changing magnetic field.
* His experiments shows that magnetic fields can create electric currents
* He showed the lines of a magnetic field by sprinkling iron filings on a piece of paper covering a magnet.
Michael Faraday (Faraday’s Law)
30
who said this?
* 2nd law of magnetic induction
* An induced current within a conductive coil produces a magnetic field to oppose the change in magnetic field which produced it
Lenz’s Law (Heinrich Friedrich Emil Lenz)
31
Who said this?
* Proposed that if a changing magnetic field can induce an electric field, then a changing electric field should induce a magnetic field
* Changing fields should move at a speed equal to the speed of light.
* The magnetic force is proportional to the product of the magnetic pole strengths divided by the square of the distance between them.
James Clerk Maxwell
32
Sl unit of magnetic field strength
Tesla
33
conventional unit of magnetic field strength
Gauss
34
magnet used in an MRI system
3 Tesla
35
1 Tesla is equivalent to?
10,000 Gauss
36
The Earth's magnetic field is approximately what at the equator
50 uT
37
The Earth's magnetic field is approximately what at the poles
100uT
38
Electricity and Magnetism were viewed as separate effects until the?
19th Century
39
observed that a dissected frog leg twitched when touched by two different metals as if it had been touched by two different metals (late 1700s).
Luigi Galvani
40
who said this
- questioned whether an electric current might be produced when two different metals are made into contact.
- He succeeded in producing a feeble electric current using zinc and copper plates.
- stacked the copper-zinc plates to form a Voltaic pile to increase the current.
Alessandro Volta
41
each zinc copper pile
Cell of a battery
42
what is
precursor to the modern battery
- paved the way to the creation of modern batteries which is an example of sources of electric potential.
Voltaic pile
43
modern dry cells use this as the positive electrode surrounded by an electrolytic paste housed in a negative zinc cylindrical can.
Carbon rods
44
electric potential is measured in units of joule per coulomb
Volts
45
The magnetic field produced by an electromagnet is the same as that produced by a bar of magnet
True
46
* An electric current is induced in a circuit if some part of that circuit is in a changing magnetic field.
* No physical motion is needed.
* If the current is increased in the electromagnet, the magnetic field will also change and induce a current in the coil
Electromagnetic Induction
47
What law states that the magnitude of the induced current depends on 4 factors:
* Strength and the Velocity of the magnetic field as it moves past the conductor
* The angle of the conductor in the magnetic field
* Number of turns in the conductor
Faraday’s law
48
What motor possesses this
* An electric current produces a mechanical motion.
* Motion of the compass needle.
* Has the same components as an electric generator.
* Electric energy is supplied to the current loop to produce motion.
* Uses many turns of wire for the current loop and many bars of magnets to create an external magnetic field
Electric Motors
49
what motor is this
* Mechanical motion induces electricity in a coil of wire.
* The motion of a magnet near a coil of wire.
* A coil of wire is places in a strong magnetic field between two magnetic poles.
* The coil is rotated by mechanical energy which in turn induces an electric current.
* The net effect of an electric generator is to convert mechanical energy into electrical energy.
Electric Generators
50
What motor is this
* The type of motor used in x-ray tubes.
* The rotating rotor is a shaft made of bars of copper and soft iron fabricated into one mass.
* The external magnetic field is supplied by several fixed electromagnets called Stators.
* Powers the rotating anode of an x-ray tube.
Induction Motor
51
devices that uses the interacting magnetic fields produced by changing electric currents
- does not convert but transforms electric potential and current into higher or lower intensity.
- Operates in alternating current.
- Has a primary turns of wire and a secondary turns of wire
Transformers
52
where input of electricity happens
Primary side
53
where output of electricity happens
Secondary side
54
If primary side has less turns of wire than the secondary side, the result will be this
Higher Voltage & Lower Current
55
the change in voltage is directly proportional to the ratio of the number of turns (windings) of the secondary coil (Ns) to the number of turns in the primary coil (Np)
Transformer Law (Voltage)
56
as the voltage changes across a transformer, the current changes also.
Transformer Law (Current)
57
Transformer that is
* Built about a square core of ferromagnetic material.
* The ferromagnetic core is not a single piece, but built up of laminated layers of iron.
* Helps reduce energy losses, resulting to greater efficiency.
Closed core transformer
58
transformer that
* Consist of an iron core with only one winding of wire about it.
* The single winding acts as the primary and secondary winding.
* Connections are made at different points on the coil for both the primary and secondary sides.
* Varies both voltage and current.
* Generally smaller and its use is restricted to cases in which a small step up or step down in voltage is required.
* Not suitable for x-ray imaging.
Autotransformer
59
* Confines even more of the magnetic field lines of the primary winding because the secondary winding is wrapped around it and there are essentially two closed cores.
* More efficient than closed-core transformer.
* Most currently used transformer
Shell type transformer
60
Does not use a ferromagnetic core to link the primary and secondary coils.
Air-core transformer
61
Primary and Secondary coils are wound on one cylinder. Magnetic path is partially through the core and partially through the surrounding air
Open-core transformer
62
* A current that opposes the magnetic field that induced it creating a loss of transformer efficiency.
* Closed-core transformer reduces this
Eddy Current
63
an additional resistance by alternate reversal of the magnetic field caused by alternating current.
Hysteresis Loss
64
* Electric current in the copper wire experience resistance.
* Results in heat generation.
Resistance