Graphite resistor is with a 10 ohm iron resistor at 20 C How large should the resistance be to be temperature independent?

To achieve temperature-independent resistance, the temperature coefficient of resistance of the material should be zero. In practice, this can be challenging, but one approach is to use a combination of materials or resistors that have opposing temperature coefficients. For a graphite resistor with a 10-ohm iron resistor at 20°C, you would need to find a specific material or design that balances the temperature changes of both components to maintain the resistance at 10 ohms across varying temperatures. The exact resistance value required will depend on the specific coefficients of the materials used.