Explain why a poor conductor whose thermal conductivity is to be determined, must be thin and fairly of large surface area. 

            Thin Sample:

• Reduced Heat Flow Path: A thinner sample ensures that the heat travels a shorter distance from the hot side to the cold side. This allows for a more accurate measurement of the temperature gradient and, consequently, the thermal conductivity.
• Minimized Thermal Resistance: A thin sample minimizes the internal thermal resistance, which helps in obtaining more precise results.

Large Surface Area:

• Enhanced Heat Transfer: A larger surface area increases the amount of heat transferred across the sample, making it easier to detect and measure the temperature change.
• Reduced Edge Effects: A larger surface area ensures that the heat flow is predominantly one-dimensional and minimizes the impact of edge effects, which can distort the measurement.

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