Electric Charge & Fields — Drills · Grade 12 Science
Chapter: Electricity, Magnetism & CircuitsWhat these drills covers
By the end of Electric Charge & Fields you should be able to:
- I can explain that charge comes in two types, is quantized, and is conserved.
- I can use Coulomb's law (F = kq₁q₂/r²) to calculate the electrostatic force between two charges.
- I can describe an electric field, calculate it with E = F/q, and sketch its field lines.
6 questions, multiple choice, numeric and written answer, each with a worked explanation.
Vocabulary used: electric charge, Coulomb's law, electric field, conductor, insulator.
Problem 1
- attract
- repel
- form a current
- have no force between them
Answer and explanation
repel
Like charges repel; only opposite charges attract.
Problem 2
Answer and explanation
40000 N/C
E = F ÷ q = 0.2 ÷ (5 × 10⁻⁶) = 40,000 N/C.
Problem 3
Answer and explanation
0.15 N
F = kq₁q₂/r² = (9 × 10⁹)(1 × 10⁻⁶)(6 × 10⁻⁶) ÷ (0.6)² = 0.054 ÷ 0.36 = 0.15 N.
Problem 4
- an insulator like glass
- a conductor like copper
- an insulator like rubber
- a vacuum only
Answer and explanation
a conductor like copper
Conductors such as copper have free electrons, so charge moves through them easily; insulators do not.
Problem 5
Answer and explanation
An electric field is the region around a charge where another charge would feel a force; its strength is the force per unit charge, E = F/q. By convention, the direction of the field at a point is the direction of the force it would exert on a small positive test charge — so field lines point away from positive charges and toward negative charges.
Problem 6
Answer and explanation
3.2 N
Force follows an inverse-square law, so halving the distance multiplies the force by 2² = 4: 0.8 × 4 = 3.2 N.