D.C. Circuits
Definitions: D.C. Circuits
- One exam question, the mark-scheme answer, and the exact phrases that score (highlighted, then listed below in the same colour).
Exam question
State Kirchhoff's first law and the quantity it conserves.
Model answer
The sum of the currents into a junction equals the sum of the currents out of it. It expresses the conservation of charge.
Marking points
1 mark each- 1sum of the currents into a junction equals the sum of the currents out(1)
- 2charge(1)
Exam question
State Kirchhoff's second law and the quantity it conserves.
Model answer
Around any closed loop, the sum of the e.m.f.s equals the sum of the p.d.s. It expresses the conservation of energy.
Marking points
1 mark each- 1sum of the e.m.f.s equals the sum of the p.d.s(1)
- 2energy(1)
Exam question
State what is meant by the internal resistance of a source and by its terminal p.d.
Model answer
The internal resistance of a source is the resistance inside the source itself. The terminal p.d. is the p.d. across the source's terminals: .
Marking points
1 mark each- 1resistance inside the source itself(1)
- 2p.d. across the source's terminals(1)