Fig. 10.1 is a diagram of a soldering iron. Solder is a mixture of metals used to make a permanent contact between electrical wires. The heating element raises the temperature of the metal tip. When solder is placed against the tip, the solder melts over the wires to be joined. When the solder cools, it solidifies and the permanent connection is made. The working temperature of the metal tip is 380 °C. [Figure 10.1] [Figure 10.2]

1. (a)The boxes in Fig. 10.2 show two materials and some different melting points. On Fig. 10.2, draw a line from the metal of the metal tip and a line from the solder to a suitable melting point for each.[2]
2. (b)(i)The heating element is rated at 24 V, 3.3A. The heating element is switched on. The temperature of the metal tip rises from 20°C to 320°C in the first 10s. Calculate the electrical energy supplied to the heating element in the first 10s.[2]
3. (b)(ii)The metal tip is made of copper and has a mass of 2.3g. The specific heat capacity of copper is 0.39J/(g°C). Calculate the thermal energy (heat) gained by the metal tip in the first 10 s.[3]
4. (c)(i)Describe, in terms of free electrons, the process by which heat transfers through the metal tip.[2]
5. (c)(ii)Heat is lost from the metal tip by convection in the air. Explain how convection occurs in the air.[2]
6. (d)(i)The temperature of the metal tip is measured with a thermocouple. In the space below, draw a labelled diagram of a thermocouple. Mark with a letter H the part of the thermocouple that is placed on the metal tip.[2]
7. (d)(ii)State two reasons why a thermocouple thermometer is suitable for measuring how the temperature of the metal tip varies during the first 10s.[2]

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