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Drift velocity, current and free-electron density (I = neAv)

This type of question, asked 2 times: 2021 Paper 7, 8 Apr 2023. All 3 questions below, oldest first.

Try each one first, then open its answer.

  1. Question 1

    2021 Paper 7

    20
    A current of 10 A10\text{ }A exists in a wire of cross-sectional area 5 mm25\text{ }mm^{2} with a drift velocity of 2×10−3 ms−12\times10^{-3}\text{ }ms^{-1}. The number of free electrons in each cubic metre of the wire is: (electronic charge =1.6×10−19 C=1.6\times10^{-19}\ C)

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  2. Question 2

    8 Apr 2023

    29
    A current of 2 A flows through a wire of crosssectional area 25.0 mm225.0{\text{ }mm}^{2}. The number of free electrons in a cubic meter are 2.0×10282.0 \times10^{28}. The drift velocity of the electrons is ____\_\_\_\_ ×10−6 ms−1\times10^{- 6}{\text{ }ms}^{- 1} (given, charge on electron =1.6×10−19C= 1.6 \times10^{- 19}C )

  3. Question 3

    8 Apr 2023

    114
    The number density of free electrons in copper is nearly 8×1028 m−38 \times10^{28}{\text{ }m}^{- 3}. A copper wire has its area of cross section =2×10−6 m2= 2 \times10^{- 6}{\text{ }m}^{2} and is carrying a current of 3.2 A. The drift speed of the electrons is___ ×10−6 ms−1\times10^{- 6}{\text{ }ms}^{- 1}.