The electrical resistance $“R”$ of a metal is given by the formula:
$$ R = p (l/A) $$
The table below shows the electrical resistance of a wire (made of metal “Z”) of length “l” and cross-sectional area “A”, at different temperatures.
|Temperature||Resistance (in ohm)|
The table below shows the resistances of wires of different lengths made out of the same metal (Z) at 20° C. The cross-sectional area of these wires is equal.
|Length (in meter)||Resistance (in ohm)|
The table below shows the resistances of wires of different cross-sectional areas made of the same metal (Z) at 20° C. The length of these wires is equal.
|Cross sectional area (in 10-8 m$^2$)||Resistance (in ohm)|
Temperature coefficient of a metal is the percentage increase in its resistance when the temperature of the metal increases by $1° \ C$. This coefficient varies with temperature.
Find the temperature coefficient of $“Z”$ at $40° \ C$.