Figure P14.66 shows a modern electronic circuit board. It features standard miniature components such as the resistor (R516), which measures 1.6 mm long, 0.80 mm wide, and 0.20 mm high. The ceramic material of the resistor has a Young’s modulus of 1.2 × 10¹⁰ Pa. When electricity flows through the circuit, the components, especially resistors, can heat up substantially. The resistor has a coefficient of thermal expansion of 2.2 × 10^-6 K^-1, and that of the circuit board it is soldered to is 6.0 × 10^-6 K^-1. 

(a) If the temperature of the circuit rises 30°C, how much longer will the circuit’s “footprint” be than the resistor that is soldered to it? 

(b) If the resistor is stretched by this amount by the circuit board, how much stress is the resistor subjected to? 

(c) The resistor has a maximum stress of 25 MPa before it will break. If a power glitch raises the temperature of the circuit by 120°C, will the resistor suffer damage from the stress?

Figure P14.66