Physics Topic 7 Flashcards
A magnet is any material or object that produces a ________ field.
magnetic
Give 3 examples of magnets:
The Earth
A horseshoe magnet
A bar magnet
The arrows on the magnetic field lines always point:
Out from the north and into the south
The strength of a magnetic field is shown by the _______ of the magnetic field lines.
density
Magnetic field lines can show (Give 2):
-> Whether two magnets would attract or repel
-> The strength of the magnet at a particular point
-> The direction that a small compass would point at that point
How can you tell which parts of the magnet diagram has the strongest magnetic field strength?
Field lines which are closer together
A magnetic m_______ is any material or object that can be influenced by a magnetic field, and has the potential to become a magnet.
material
Which of the following elements are magnetic?
Iron
Nickel
Copper
Cobalt
Iron
Nickel
Copper
Cobalt
Which type of magnetism is it when a magnetic material temporarily becomes a magnet when it’s placed close to a permanent magnet?
Induced magnetism
Permanent magnets always produce their ___ magnetic field
Temporary / induced magnets only produce a magnetic field in the ________ of another magnet
Permanent magnets always produce their own magnetic field
Temporary / induced magnets only produce a magnetic field in the presence of another magnet
The force between a permanent and an induced magnet will:
Always be attractive
Magnetic materials that gain and lose magnetism quickly are called magnetically ____ materials.
Magnetic materials that gain and lose magnetism slowly are called magnetically ____ materials.
soft
hard
An example of a magnetically soft material is ____.
And example of a magnetically hard material is _____.
iron
steel
When an e_______ current flows through a material, a magnetic field is always p_______
electrical
produced
The right hand rule can tell us the…
… direction of the magnetic field induced by a flowing current.
In the _____ ____ rule, the thumb is placed following the same direction as the c______ is travelling, and the fingers are the curled in the direction of the magnetic field l____.
right hand
current
lines
In an electromagnet, a current is required to produce the magnetic field.
When the current is switched off, the magnetic field:
disappears
Describe the 3 ways to increase the strength of an electromagnet.
Increase the current
Increase the number of turns in the solenoid, while keeping the length the same
Reduce the length of the solenoid while keeping the number of turns the same
Add a soft iron core
What is the motor effect?
A current carrying wire in the presence of a magnetic field will experience a force.
To experience the full force, a current carrying wire must be placed _____________ to the magnetic field.
perpendicular
Fleming’s left hand rule can be used to tell us…
… the direction of the force experienced by a current carrying wire in a magnetic field.
Fleming’s Left Hand Rule)
The thumb represents…
The direction of the force
Fleming’s Left Hand Rule)
The index represents…
The direction of the magnetic field
Fleming’s Left Hand Rule)
The middle represents…
The direction of the current
The magnetic field strength (also known as magnetic flux density) is measured in:
Teslas (T)
A wire carrying a current of 2 A is perpendicular to a magnetic field of 15 T. The length of the wire in the field is 0.2 m.
What is the force experienced by the wire?
2 x 15 x 0.2 = 6N
A wire carrying a current of 6 A is perpendicular to a magnetic field of 30 T. The length of the wire in the field is 0.1 m.
What is the force experienced by the wire?
6 x 30 x 0.1 = 18N
How does the split ring commutator ensure the coil rotates in one direction? 4 steps
1) The split-ring commutator swaps the positive and negative connections every half turn.
2) Therefore, the direction of the current through the coil reverses every half turn.
3) This means that the forces acting on the coil will always be acting in the same direction.
4) This causes the coil to rotate continuously in one direction.
Overall, electric motors use e__________ to create a rotational m_____.
electricity
motion
Give 2 ways to increase the speed of rotation in an electric motor:
Add more turns to the coil
Increase the magnetic field strength / magnetic flux density of the magnet
Increase the current in the coil
