Charge questions

1.  What exactly *is* charge?  How do we think of it?  How does this relate to protons and electrons, etc.?

2.  Why is it that electrons are the easiest particles to manipulate?

3.  What does atomic number (Hydrogen = 1, Helium = 2, etc.) mean?

4.  What are quarks?

5.  Coulomb's law is an "inverse square law" - what does this mean exactly?

6.  Why can a charged balloon stick to a wall?

7.  What is "grounding"?

8.  Recall the demonstration where I charged up the small suspended piece - what was I showing?

Comments

Post a Comment

Popular posts from this blog

Newton's take on Gravitation - the inverse square law

Image
Newton's take on gravity and orbits - which is the genesis of our modern conception of it, is based on: Universal Gravitation (1687, Principia) Newton's take on orbits was quite different. For him, Kepler's laws were a manifestation of the bigger "truth" of universal gravitation. That is: All bodies have gravity unto them. Not just the Earth and Sun and planets, but ALL bodies (including YOU). Of course, the gravity for all of these is not equal. Far from it. The force of gravity can be summarized in an equation: or.... the force of gravitation is equal to a constant ("big G") times the product of the masses, divided by the distance between them (between their centers, to be precise) squared. Big G = 6.67 x 10^-11, which is a tiny number - therefore, you need BIG masses to see appreciable gravitational forces. This is an INVERSE SQUARE law, meaning that: - if the distance between the bodies is doubled, the force becomes 1/4 of its ...
Read more

Lenses and how they form images

Image
Lenses As shown and discussed in class, light refracts TOWARD a normal line (dotted line on the left image, perpendicular to surface of lens) when entering a more dense medium. Note in this  convex  lens that this direction of bend changes from down (with the top ray) to up with the bottom ray. This is due to the geometry of the lens. Look at the picture to make sure that this makes sense.  As a result, the rays will intersect after leaving the lens.  An image can form! The FOCAL LENGTH (f) of a lens (or curved mirror) where the light rays would intersect, but ONLY IF THEY WERE INITIALLY PARALLEL to each other. Otherwise, they intersect at some other point, or maybe not at all (if the object is too close to be focused on)! Note that your (human) eye lenses are convex - slightly thicker in the middle.  Thus, your eyes form "real" images on the retina - upside-down!  Unless, of course, the object is too close. If an image is projected onto ...
Read more

Electromagnetism and Electromagnetic Induction

Image
Electromagnetism Recall that the motion of charges leads to magnetic fields.   If you have charge traveling through a wire, electrons can be thought of as moving together – this causes a magnetic field, also known as electromagnetism.  The magnetic field caused by a current passing through a wire is often small, but if you coil the wire upon itself, the magnetic fields “add up”.  Several hundred turns of wire (with current running through it) can produced quite a strong electromagnet.  A coil with current running through it can naturally react to a permanent magnet – if this is engineered well, we have a motor.  See illustrations and demos in class. Below:  basic motors Electromagnetic Induction So, current causes magnetism – something shown in the early 19 th  century by Hans Oersted.  As it happens, the reverse is also true – magnetism can cause current, but there must be some relative CH...
Read more