Cambridge International AS & A Level · 9 · structured
Compare metal, diode and filament-lamp characteristics
Compare metal, diode and filament-lamp characteristics · Original GioPhysics question with a detailed, mark-by-mark answer guide.
- Demand
- demanding
- Marks
- 13
- Topics
- 4
- Answer
- Complete
For each sketch use horizontal potential difference V and vertical current I, showing both voltage signs. A filament lamp operates at 2.0 V,0.40 A and later at 6.0 V,0.60 A; assume steady thermal conditions at each operating point.
- (a)
Define resistance and determine it at the two lamp operating points. Explain why these are V/I ratios, not simply the slope of an I–V curve.
3 marks - (b)
Sketch and label I–V characteristics for a metallic conductor at constant temperature, a diode below reverse breakdown, and a filament lamp. Explain the distinguishing shape of each.
6 marks - (c)
State Ohm's law with its physical condition. Explain microscopically why the filament's resistance rises as current grows, and why a lamp is not an ohmic resistor over the full voltage range.
4 marks
Ready to self-mark?Reveal the detailed answer guide
(a)
Define resistance and determine it at the two lamp operating points. Explain why these are V/I ratios, not simply the slope of an I–V curve.
List the given quantities with units, identify the required quantity, write the governing relationship before substituting, and keep extra digits until the final line so rounding does not distort the result.
- 1
Define p.d./current at the stated operating point.
- 2
Calculate2.0/0.40 and6.0/0.60.
- 3
Distinguish static ratio from graph tangent.
(b)
Sketch and label I–V characteristics for a metallic conductor at constant temperature, a diode below reverse breakdown, and a filament lamp. Explain the distinguishing shape of each.
Identify what the question is testing, organise the response into distinct mark-earning points, and make every conclusion traceable to a physical principle or to the evidence supplied.
- 1
Draw constant-temperature metal line through origin.
- 2
Draw diode strongly asymmetric, without implying large reverse conduction below breakdown.
- 3
Draw lamp curve flattening with increasing positiveV and point-symmetric negative branch.
- 4
LabelI,V axes and identify each curve; do not swap I andV.
(c)
State Ohm's law with its physical condition. Explain microscopically why the filament's resistance rises as current grows, and why a lamp is not an ohmic resistor over the full voltage range.
Identify what the question is testing, organise the response into distinct mark-earning points, and make every conclusion traceable to a physical principle or to the evidence supplied.
- 1
State proportionality and constant temperature/physical conditions.
- 2
Connect higher electrical heating to temperature increase.
- 3
Connect lattice vibration to greater carrier scattering.
- 4
Link changingR to non-straightI–V response.
Complete marking guidance
Use these worked steps alongside the part-by-part answers. They explain the method and mark allocation; they do not add extra marks.
- (a) Define p.d./current at the stated operating point.
- (a) Calculate2.0/0.40 and6.0/0.60.
- (a) Distinguish static ratio from graph tangent.
- (b) Draw constant-temperature metal line through origin.
- (b) Draw diode strongly asymmetric, without implying large reverse conduction below breakdown.
- (b) Draw lamp curve flattening with increasing positiveV and point-symmetric negative branch.
- (b) LabelI,V axes and identify each curve; do not swap I andV.
- (c) State proportionality and constant temperature/physical conditions.
- (c) Connect higher electrical heating to temperature increase.
- (c) Connect lattice vibration to greater carrier scattering.
- (c) Link changingR to non-straightI–V response.
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