IB Physics SL B.5.12 Resistance & resistivity

Practise using R = ρL/A to calculate resistance or resistivity, compare geometry changes, and check correct derived SI units.

Exam points

calculate resistivity from resistance, length and area, then state the unit as Ω m
compare reshaped conductors by tracking how length and cross-sectional area change in R = ρL/A
determine how diameter or area changes alter resistance when the material stays the same

[Maximum number: 3]

Part 2 Electric current and resistance
The graph below shows how the current I in a tungsten filament lamp varies with potential difference V across the lamp.

Figure for Question B.5.12—Resistance and resistivity question 1 — IB Physics SL

The length of the filament in a lamp is 0.40 m . The resistivity of tungsten when the potential difference across it is 2.8 V is $5.8 \times 10^{-7} \Omega \mathrm{~m}$ . Calculate the radius of the filament.

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B.5.12—Resistance and resistivity question 1