A magnetic field of flux density 
is normal to face PQRS of a slice of a conducting material, as shown in the figure below.
A current 
in the slice is normal to face QRZY of the slice. The Hall voltage 
across the slice is given by the expression
State what is represented by the symbol 
.
The symbol 
represents the length of one side of the slice. Use letters from the figure above to identify .
In general, the Hall voltage produced in a slice of a metal is very small. For a slice of the same dimensions with the same current and magnetic flux density, the Hall voltage produced in a semiconductor material is much larger. Suggest and explain why.
