Electromagnetism Flashcards
(120 cards)
1
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Flashcard 1:
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2
Q
front: How does the Earth act in terms of magnetism?
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3
Q
back: The Earth acts like a giant bar magnet
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with a magnetic field extending around it.
4
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Flashcard 2:
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5
Q
front: In which direction do magnetic field lines always go?
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6
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back: Magnetic field lines always go from north to south.
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7
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Flashcard 3:
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8
Q
front: What does the arrow on a magnetic field line indicate?
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9
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back: The arrow on a field line indicates the direction a free north pole would move.
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10
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Flashcard 4:
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11
Q
front: What does it mean when magnetic field lines are equally spaced and parallel?
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12
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back: Equally spaced and parallel field lines indicate a uniform magnetic field.
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13
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Flashcard 5:
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14
Q
front: What is the field pattern between two opposing magnetic poles?
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15
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back: The field pattern between two opposing poles can be approximated as uniform
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with field lines going from north to south.
16
Q
Flashcard 6:
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17
Q
front: How do magnetic field lines behave between like poles?
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18
Q
back: Field lines curve away from each other between like poles
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and all field lines aim towards the south pole.
19
Q
Flashcard 7:
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20
Q
front: What kind of magnetic field is generated around a current-carrying wire?
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21
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back: A current-carrying wire generates a magnetic field of concentric circles around it.
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22
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Flashcard 8:
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23
Q
front: What does the symbol ⊗ represent in current notation?
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24
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back: The symbol ⊗ represents current going into the screen or page.
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Flashcard 9:
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front: What does the symbol ⊙ represent in current notation?
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back: The symbol ⊙ represents current coming out of the screen or page.
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Flashcard 10:
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front: If the current goes into the screen
what is the direction of the magnetic field around the wire?
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back: If the current goes into the screen
the magnetic field goes in a clockwise direction.
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Flashcard 11:
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front: If the current comes out of the screen
what is the direction of the magnetic field around the wire?
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back: If the current comes out of the screen
the magnetic field goes in an anti-clockwise direction.
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Flashcard 12:
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front: What is the Right Hand Grip Rule for determining magnetic field direction?
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back: Imagine gripping the wire with your right hand: your thumb points in the direction of the conventional current
and the curl of your fingers shows the direction of the magnetic field lines.
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Flashcard 13:
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front: Which hand should always be used for the Right Hand Grip Rule?
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back: The right hand should always be used.
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Flashcard 14:
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front: What direction should be considered for current when using the Right Hand Grip Rule?
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back: Use the direction of conventional current when applying the rule.
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Flashcard 15:
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front: In a wire with current flowing upwards
what is the direction of the magnetic field at point A if point A is around the wire?
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back: At point A
the magnetic field comes out of the screen or page.
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Flashcard 16:
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front: In the same scenario
what is the direction of the magnetic field at point B around the wire?
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back: At point B
the magnetic field goes into the screen or page.
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Flashcard 17:
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front: How can the magnetic field inside a solenoid be described?
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back: The magnetic field inside a solenoid can be assumed to be uniform.
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Flashcard 18:
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front: What determines the location of the north and south poles in a solenoid?
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back: The direction of the current determines the location of the north and south poles.
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Flashcard 19:
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front: What happens to the poles of a solenoid if the current direction is reversed?
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back: If the current direction is reversed
the poles are also reversed.
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Flashcard 20:
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front: What happens to a wire of length \( l \) carrying current \( I \) within an external magnetic field of magnetic flux density \( B \)?
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back: The wire experiences a magnetic force.
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Flashcard 21:
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front: What is the formula for the magnetic force on a current-carrying wire within a magnetic field?
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back: The magnetic force \( F = B I l \sin(\theta) \)
where \( \theta \) is the angle between the wire and the magnetic field.
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Flashcard 22:
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front: When a charged particle moves in a circle in a magnetic field
how is the magnetic force related to the centripetal force?
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back: The magnetic force is set equal to the centripetal force to analyze the motion.
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Flashcard 23:
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front: What is magnetic flux?
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back: Magnetic flux is the product of the magnetic flux density perpendicular to an area and the area itself.
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Flashcard 24:
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front: What is the component of the magnetic flux density that is important for calculating magnetic flux?
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back: The component of magnetic flux density perpendicular to the surface area.
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Flashcard 25:
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front: If the angle between the magnetic field and the normal to the surface is \( \theta \)
how is the perpendicular component of the magnetic field expressed?
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back: It is expressed as \( B \cos(\theta) \).
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Flashcard 26:
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front: What is the formula for magnetic flux \( \phi \)?
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back: \( \phi = B A \cos(\theta) \)
where \( B \) is magnetic flux density
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Flashcard 27:
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front: Is \( \theta \) the angle to the surface or the angle to the normal when calculating magnetic flux?
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back: \( \theta \) is the angle to the normal
not the surface itself.
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Flashcard 28:
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front: When is the magnetic flux through an area at its maximum?
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back: Magnetic flux is maximum when the magnetic field is perpendicular to the area
meaning \( \theta = 0^\circ \).
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Flashcard 29:
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front: When is the magnetic flux through an area zero?
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back: Magnetic flux is zero when the magnetic field is parallel to the area
meaning \( \theta = 90^\circ \).
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Flashcard 30:
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front: How is magnetic flux density \( B \) measured?
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back: Magnetic flux density is measured in Teslas (T).
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Flashcard 31:
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front: How is magnetic flux \( \phi \) measured?
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back: Magnetic flux is measured in Webers (Wb).
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Flashcard 32:
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front:State Faraday's law of electromagnetic induction:
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back: The magnitude of the induced emf across the ends of a conductor is directly proportional to the rate of change in the magnetic flux linkage with the conductor.
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Flashcard 33:
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front: Define:-The Magnetic flux
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back: Define:-The Magnetic flux
the induced current flows in a direction so as to set up to oppose the change in the magnetic flux.
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Flashcard 34:
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front: What does Faraday's Law state regarding induced electromotive force?
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back: The magnitude of the induced EMF is directly proportional to the rate of change of magnetic flux linkage.
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Flashcard 35:
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front: Write the mathematical expression of Faraday's Law for induced EMF.
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back: \( E = -\frac{\Delta (N \phi)}{\Delta t} \)
where \( E \) is the induced EMF.
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Flashcard 36:
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front: What does the negative sign in Faraday's Law represent?
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back: The negative sign represents Lenz's Law
indicating the induced current opposes the change producing it.
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Flashcard 37:
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front: What does Lenz's Law state about the direction of induced current?
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back: Lenz's Law states that the induced current's direction is such that it opposes the change in magnetic flux that produced it.
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Flashcard 38:
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front: Give an example illustrating Lenz's Law.
114
back: If a north pole of a magnet approaches a copper wire
the wire generates a current making it an electromagnet with its own north pole facing the magnet
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Flashcard 39:
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front: What happens to the angle between the normal to a coil and the magnetic field in an AC generator?
117
back: The angle changes as the coil rotates in the magnetic field.
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Flashcard 40:
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front: Write the expression for EMF induced in a rotating coil (AC generator).
120
back: \( E = -\frac{\Delta (N B A \cos(\theta))}{\Delta t} \)
where \( N \) is number of turns
