IB Physics SL B 1 10 Thermal Transfer Mechanisms Questions

Practise conduction, convection and radiation using insulation, surfaces, fluids and planetary energy pathways in exam questions.

Exam points

Distinguish conduction, convection and thermal radiation as primary mechanisms of thermal-energy transfer.
Relate each mechanism to particle motion, bulk-fluid motion or electromagnetic emission and select the mechanism supported by complete evidence.

[Maximum number: 3]

An electrically heated pad is designed to keep a pet warm.

The pad is heated using a resistor that is placed inside the pad. The dimensions of the resistor are shown on the diagram. The resistor has a resistance of $4.2 \Omega$ and a total length of 1.25 m .

Figure for Question IB Physics SL B 1 10 Thermal Transfer Mechanisms Questions question 1 — IB Physics SL

When there is a current in the resistor, the temperature in the pad changes from a room temperature of $20^{\circ} \mathrm{C}$ to its operating temperature at $35^{\circ} \mathrm{C}$ .

The design of the pad encloses the resistor in a material that traps air. The design also places the resistor close to the top surface of the pad.

Explain, with reference to thermal energy transfer, why the pad is designed in this way.

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IB Physics SL B 1 10 Thermal Transfer Mechanisms Questions question 1