magnetism science chap 7 1 3 2 4 5 7 6 8 910 1112 1314 1 3 2 4 5 7 6 8 910 1112 1314
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Magnetism
Science Chap 7
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Use the control buttons on the right to move from item to item in any order. Use the control buttons on top to flip card or move through the cards one at a time.
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Gold: Questions
Orange: Answers
First Previous Flip Next Last
Help Page Return
Q1
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Name ways to make an electric motor more powerful by making its magnet stronger?
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A1
These are a few ways to make an electric motor more powerful:
Use a larger current flowing through the coil.
Increase the number of turns of wire around the coil.
Use a soft-iron core in the middle of the coil.
Use stronger magnets, such as electromagnets either side of the coil.
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13 142
Explain how the acronym:
My Fine Clothes
Can be used to remember the left-hand rule that is used with motors?
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My = Thumb to remember Motion of wire
Fine = First finger to remember Field
Clothes = Second finger to remember Current
Place fingers at 90 degrees from each other.
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Apply the left-hand rule to the following drawing. Where does your thumb, first and second fingers point to?
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Current = Second finger points in direction of current
Field = First finger points in direction of field (North to South)
Motion = Thumb points up so wire moves upwards.
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When a current flows through a wire it produces a: (finish the sentence)
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When a current flows through a wire it produces a magnetic field.
Red wire is positive so it is the north pole. Do you notice that the compasses point away from the north?
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13 145
The simplest type of electromagnet is a coiled piece of wire. A coil forming the shape of a straight tube (similar to a corkscrew). What is this typeof electromagnet called?
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It is called a solenoid. The current of negative flows to the positive. The north pole will be positive.
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13 146
In the two following diagrams of cobalt. Explain which will be magnetic and what term is used to described the little rods that are part of atoms.
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In the case of the domains that are not organized, the cobalt will not be magnetic.
In the case of the domains that are organized, the cobalt will be magnetic. They become organized if a magnet comes close to the piece of cobalt.
A domain is the ordering of electron spins. When they are organized in the same spin then they create magnetism.
unorganized
organized
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A
B
What terms are used to describe case A and case B
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A
B
Case A is: attraction
Case B is: repulsion
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13 148
Draw the representation of the direction of the magnetic field around the Earth.
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The red part in each compass indicated the north. The field travels from north toward the south.
Therefore the geographical north is the magnetic south.
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13 149
Use the two following pictures to explain the term ferromagnetic. Also state which three elements are known to be ferromagnetic.
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Iron, nickel, cobalt are some common elements that show a unique magnetic behavior which is called ferromagnetism.
Ferromagnetic materials have their unpaired electron spins to line up parallel with each other in a region called a domain if externally imposed magnetic field, say from a solenoid.
Domains can align causing magnetism.
Ferromagnets will tend to stay magnetized to some extent after being subjected to an external magnetic field.
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In the above left diagram, using the left-hand rule, what will be the direction of the current flow when the switch closes?
Sometimes you meet two ideas of current: conventional current and electron current.
Which current does the left-hand rule uses?
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The purple line indicates the current used with the left-hand rule.
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+
_
Use the left-hand rule to indicate the current, the motion and the direction of the field.
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Remember that the electron flow is the current.
The flow goes from north to south.
The motion is upwards.
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Use the left-hand rule to show the current, the motion and the field.
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Thumb = motion ( in this case downward)
First finger = field
Second finger = current
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The END(exit program)
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13 14Paul Widergren © 2004
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