Unit 4 - Lesson 6: Magnetism and Electromagnetism Flashcards
What materials do magnets exert a force on?
Magnetic materials like iron, nickel, cobalt, and steel.
What materials do magnets not exert a force on?
Materials don’t exert a force on non-magnetic materials (plastic, paper & rubber).
What are the poles that most magnets have called? What are poles? How does the attraction and repellent of poles work?
A north and south pole. Poles are the strongest part of the magnet. Opposite poles attract each other. Same poles repel each other. So, North and North poles repel each other, whereas North and South poles attract each other.
What type of magnetic materials keep their magnetism? What do we call these types of magnets?
Hard magnetic materials like steel keep their magnetism. They’re not automatically magnetic. They’re difficult to magnetise, but once magnetic, keep it. We call them permanent magnets (even though you can demagnetise them).
What type of magnetic materials lose their magnetism? What do we call these types of magnets? How do these magnets work in the range of a permanent magnet?
Soft magnetic materials easily lose their magnetism. They’re temporary magnets e.g. iron. A temporary magnet’s magnetism is induced by a permanent magnet. If a temporary magnet enters the magnetic field of a permanent magnet, it’s magnetised. Outside the magnetic field, it loses magnetism. This magnet is an induced magnet. The poles (polarity) of the induced magnet depends on the position of the poles on the permanent.
What do magnetic lines show?
How far force spreads (space where magnetism is detected)
Can magnetic objects feel the force outside the magnetic field lines?
No. Magnetic objects can only feel the force if they come within the magnetic field lines.
Where are magnetic lines always directed from?
Lines are always directed from north to south.
What does the number of magnetic lines show?
The strength of the magnet.
Is magnetism at the poles stronger or weaker than away from the poles?
Stronger.
Draw the magnetic field (with magnetic lines) for two bar magnets close but not touching with
a) Like poles
b) Opposite poles/Unlike poles
a) https://i.pinimg.com/736x/b4/04/5b/b4045b9667b04c6c0e8fa14a17d20621.jpg
b) https://i.pinimg.com/736x/c1/8c/03/c18c03de1419aff692315edcc142390f.jpg
What is a uniform magnetic field pattern?
It’s when the lines in a magnetic field are straight and evenly spaced. The lines directly between the unlike poles are straight and evenly spaced, this is an example of a uniform magnetic field pattern.
What is the same in a uniform magnetic field pattern?
The strength and direction of the field is the same everywhere in a uniform magnetic field pattern.
Where do we see uniform fields?
Between any north and south poles if they’re directly opposite each other. They must be close but not touching.
What are uniform magnetic fields useful for making?
Motors.
When do magnetic fields overlap?
When two magnets move close to each other, the fields overlap.
Draw overlapping magnetic fields. Remember that you’ll always have a straight line between two opposite poles (facing each other). Also, field lines move from north to south.
https://i.pinimg.com/736x/cc/1f/53/cc1f53c9f5278e198f77408bda3bcacf.jpg
Do field lines move from north to south OR south to north?
Field lines move from north to south.
Draw the field pattern for same poles next to each other.
https://i.pinimg.com/736x/4f/81/f6/4f81f6fa2d17c49f8ebaa674682622f6.jpg
(The second one is the correct one for same poles next to each other).
CORE PRACTICAL: Investigate the magnetic field patterns of bar magnets.
There are 2 ways we can show the shape, direction and strength of a magnetic field.
a) What is the first method?
b) What apparatus is needed?
c) What is the second method?
d) What apparatus is needed?
a) Using Iron Fillings:
1. Place the bar magnet on a table underneath the paper.
2. Tap paper gently to reveal shape.
3. Observe the lines. The closer the lines are, the stronger the magnetism. The lines show how far the magnetism extends. The direction of a line is always from the north to south pole of the magnet. In reality, the field is spreading out in all direction (3D).
b) Bar magnet, paper, iron fillings
c) Using A Compass:
1. Place a magnet on a piece of paper.
2. Place a compass at the north end of the magnet.
3. Mark, with a pencil, an arrow on the paper pointing in the direction of the needle. This is the direction of the field line.
4. Repeat in a slightly different place.
