Charging of bodies. Electric charge
Answers are for parents and teachers.
1
Give an example (comb and paper) of an electrified body attracting neutral light objects and describe what you see.
Once the comb is electrified, light paper scraps are pulled to it; without rubbing there is no attraction.
2
A beryllium atom has 4 protons. How many electrons does the neutral atom have, and what is their total charge in units of e?
4 electrons; total charge –4e.
3
A body receives 2.5·10¹¹ electrons. What is its charge? (e = 1.6·10⁻¹⁹ C)
q = 2.5·10¹¹ · 1.6·10⁻¹⁹ = 4·10⁻⁸ C, negative.
4
Classify as conductor or dielectric: graphite (pencil lead), a plastic ruler, dry wood.
Graphite — conductor; plastic ruler — dielectric; dry wood — dielectric.
5
Describe how to make a simple electroscope at home from a glass jar, lid, aluminium wire and foil. Do you need an adult’s help?
Pierce the lid and pass the wire through, hang foil leaves on the inner end; an adult helps with piercing and cutting the wire.