Exam-style question
Try this first
In a circuit with a filament lamp, which of the following statements about the I‑V curve is true?.
- A.The curve passes through the origin and is a straight line.
- B.The curve does not pass through the origin and is a straight line.
- C.The curve passes through the origin and is curved.
- D.The curve does not pass through the origin and is curved.
Model answer
What a good answer should say
- The curve does not pass through the origin and is curved.
Explanation
Why this works
A filament lamp is a non‑ohmic device. Its I‑V curve does not go through the origin because the filament has a finite resistance even at zero applied voltage (due to its temperature).
The curve is also curved because resistance changes with temperature as current flows, making the relationship non‑linear.
Common mistake
No common mistake is linked to this question yet.