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Question 18M.2.HL.TZ1.4c.ii

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Date May 2018 Marks available [Maximum mark: 3] Reference code 18M.2.HL.TZ1.4c.ii
Level HL Paper 2 Time zone TZ1
Command term Show that Question number c.ii Adapted from N/A
c.ii.
[Maximum mark: 3]
18M.2.HL.TZ1.4c.ii

An ohmic conductor is connected to an ideal ammeter and to a power supply of output voltage V.

M18/4/PHYSI/SP2/ENG/TZ1/04

The following data are available for the conductor:

                    density of free electrons     = 8.5 × 1022 cm−3

                    resistivity                          ρ = 1.7 × 10−8 Ωm

                    dimensions           w × h × l = 0.020 cm × 0.020 cm × 10 cm.

 

The ammeter reading is 2.0 A.

The electric field E inside the sample can be approximated as the uniform electric field between two parallel plates.

(c.ii)

Show that  v E = 1 n e ρ .

[3]

Markscheme

ALTERNATIVE 1

clear use of Ohm’s Law (V = IR)

clear use of R = ρ L A

combining with I = nAve and V = EL to reach result.

 

ALTERNATIVE 2

attempts to substitute values into equation.

correctly calculates LHS as 4.3 × 109.

correctly calculates RHS as 4.3 × 109.

 

For ALTERNATIVE 1 look for:

V = IR

R =  ρ L A

V = EL

I = nAve

V = I ρ L A

EL = I ρ L A

E = I ρ A

E = nAve ρ A = nveρ

v E = 1 n e ρ

[3 marks]

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