# IB Physics Electric Current

A tutorial sheet of electric current questions is given below.

1. The density of copper is 8960 kgm-3. If the molar mass of copper is 63.5 g, determine the number of free electrons per cubic metre of copper if each atom provides one free electron. [8.5x1028]
2. Determine the electron drift speed in a copper wire of diameter 2.0 mm carrying a current of 1.0 A.
3. List some common metals that have a free electron density greater than that of copper.[aluminium, iron, magnesium, tin, lead, zinc, magnesium]
4. What is meant by a free electron?
5. Explain why a wire heats up when a current passes through it.
6. A student in an answer states that "resistance in a copper wire is due to collisions between the electrons and the positively charged copper atoms". Analyse this statement.
7. Two metal wires are made of the same material and are at the same temperature. The potential difference across each wire is the same. If the length of the second wire is one-half that of the first wire and the diameter of the first wire is two times that of the second wire in which wire does a greater current flow?
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