Tip:
Highlight text to annotate it
X
So what I would like to do for you now is a demonstration to
introduce the concept of magnetism.
So we are getting ready to begin the lesson on
electrical, optical, and magnetic properties.
And I want to demonstrate a specific property of magnetism
by magnetizing a grape.
And so you might ask yourself, wow, are grapes magnetic?
And the answer is no.
But they will act as a magnet if you place them in the
presence of a strong magnetic field.
And this property of not being magnetic, but acting as a
magnet in the presence of a strong magnetic field, is
called paramagnetism.
So you will learn in this lesson that there are three
main categories of magnetism that we're interested in.
There's the ferromagnetism, paramagnetism, and
diamagnetism.
And so these grapes are going to exhibit paramagnetism.
And so the strong magnetic field is going to be produced
by this neodymium magnet that I actually borrowed from a
hard drive that no longer works.
And this magnet I'm going to use to push the grapes around
in a circle by exposing them to this magnetic field.
And you can see the grapes are not swinging or moving any on
their own right now.
And now let's show the magnetic field to the grapes.
And what you will see is that I am not touching the grapes.
But yet I'm pushing them around in a circle.
What's happening here, it's not that the grape is
paramagnetic.
It's the fact that the grape is 70% water.
And water is paramagnetic.
And so what's happening is the water sees the magnetic field
from this neodymium magnet.
And they're perturbed by that.
And to show their distaste, they all align to resist the
magnetic force of this magnet.
So it's essentially like putting two north ends of a
magnet together.
So let me show you this one more time.
So I'm going to get it going in a circle.
And then, once I have it sufficiently moving, I'll stop
it and get it going in the opposite direction.
And as you will see, I am not touching the grape.
So we have just magnetized a grape.