1. How do electrical charges behave
Topic 3.2

2. Topic 3.2 Key Concepts
Electrons carry a negative charge, and protons carry a positive charge
Opposite charges attract each other, and like charges repel each other

3. Concept 1: Electrons carry a negative charge; Protons carry a positive charge
- can be rubbed off a material
The charges of
Surround the
- left behind when negative charges are rubbed off a material
Part of the of atoms
Held firmly in place, unlike electrons, so they cannot be rubbed off
Negative charge
electrons
nucleus
Positive charge
protons
nucleus

4. Negative & Positive charges
When electrons are rubbed off a material, the material becomes
charged
That material that electrons becomes charged
Charging material by rubbing is called
Whether a material gains or loses electrons depends on the combination of materials
Negative & Positive charges
positively charge
gains
negatively
charging by friction

5. Electrically neutral & electrically charged materials
- before 2 materials are rubbed together, they have numbers of positively charged protons and negatively charged electrons
The positive and negative charges cancel out, leaving the material
- if electrons are rubbed off, the protons stay behind, making the material
The material gaining electrons is also electrically charged
Being electrically charged means there is an number of positive and negative charges
Uncharged materials
equal
neutrally charged
Charged materials
positively charged
unequal

6. Explain the relationships among negative charges, positive charges, electrons, and protons.
Describe what sometimes happens in terms of charges when you rub 2 different types of materials together.
Discussion questions

7. Concept 2: opposite charges attract & like charges repel
– summarizes the properties of charges (how charges interact with each other) 1)
Every negative charge attracts every positive 2)
Every negative charge repels every other negative charge; every positive charge repels every other positive charge
Law of Electric Charge
Opposite charges attract each other
Like charges repel each other
Phet activity

8. Concept 2: opposite charges attract & like charges repel
Why does a charged balloon stick to an electrically neutral wall?
when a object (balloon) is brought near a object (wall), the in the neutral object do not come off
Negative charges in the wall are from the surface by the negative charges on the balloon
Positive ends of the molecules in the wall are to the negative charges on the balloon
This attraction is strong enough to hold the balloon to the wall
charged
neutral
electrons
pushed
away
Phet activity
attracted

9. Discussion questions State the law of electric charge.
Make a labeled sketch, including charges, to explain why a stream of neutral water bends towards a positively charged comb
Discussion questions