Work through the list without notes. If you cannot do a statement, follow its link, then come back. Guide = study guide; Practice = practice questions.
Understanding
- I can describe charge as a scalar with two signs, and give the charges of the proton, electron and neutron. (Guide: “What electric charge is”)
- I can explain that any object’s charge is a whole-number multiple of e, and that objects charge by gaining or losing electrons. (Practice Q2)
- I can say when an object may be modelled as a point charge. (Guide: “What electric charge is”)
- I can explain polarisation, permittivity and the difference between conductors and insulators. (Guide: Figure 2; Practice Q6)
- I can explain why everyday contact forces are electric in origin. (Practice Q6)
Calculation and skills
- I can use Coulomb’s law with SI units to find the size of the force between two point charges. (Practice Q4, Q5)
- I can decide the direction of each force from the signs and draw it along the line joining the charges. (Guide: Figure 1)
- I can add forces from up to four charges using components and give the magnitude and direction of the net force. (Guide: Worked example 1; Practice Q4)
- I can calculate the ratio of electric to gravitational force for two particles. (Practice Q3, Q5)
- I can find the point on a line where the net force on a third charge is zero. (Guide: Worked example 2; Practice Q7)
Reasoning
- I can predict the factor by which the force changes when charges or separation change. (Practice Q1, Q5)
- I can explain why gravity dominates at large scales even though the electric force is far stronger between particles. (Guide: “Electric force versus gravitational force”; Practice Q6)
- I can use the sign of dF/dx, or the forces on each side, to decide whether a balance point is stable. (Guide: Worked example 2; Practice Q7)
All ticked? Move on to Conservation of Electric Charge and the Process of Charging, or return to the course roadmap.