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Question 18N.2.HL.TZ0.a

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Date November 2018 Marks available [Maximum mark: 3] Reference code 18N.2.HL.TZ0.a
Level HL Paper 2 Time zone TZ0
Command term Calculate Question number a Adapted from N/A
a.
[Maximum mark: 3]
18N.2.HL.TZ0.a

A lighting system consists of two long metal rods with a potential difference maintained between them. Identical lamps can be connected between the rods as required.

The following data are available for the lamps when at their working temperature.

 

Lamp specifications                      24 V, 5.0 W

Power supply emf                         24 V

Power supply maximum current   8.0 A

Length of each rod                       12.5 m

Resistivity of rod metal                 7.2 × 10–7 Ω m

Each rod is to have a resistance no greater than 0.10 Ω. Calculate, in m, the minimum radius of each rod. Give your answer to an appropriate number of significant figures.

[3]

Markscheme

ALTERNATIVE 1:

r = ρ l π R OR  7.2 × 10 − 7 × 12.5 π × 0.1  ✔

r = 5.352 × 10−3 ✔

5.4 × 10−3 «m» ✔

 

For MP2 accept any SF

For MP3 accept only 2 SF

For MP3 accept ANY answer given to 2 SF

 

ALTERNATIVE 2:

A = 7.2 × 10 − 7 × 12.5 0.1  ✔

r = 5.352 × 10−3 ✔

5.4 × 10−3 «m» ✔

 

For MP2 accept any SF

For MP3 accept only 2 SF

For MP3 accept ANY answer given to 2 SF

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