Microwave miscellany
Stories from Physics
for 11-14
14-16
- Salty foods may warm up slightly more quickly than food without seasoning in a microwave oven. Although the main mechanism by which food is heated is through the absorption of microwaves by water molecules, in solution, Na+ and Cl- ions experience a force due to the changing electric and magnetic. Hence salty water will heat faster than pure water in a microwave.
- Melting ice in a microwave oven is a slow process because ice has different dielectric properties from liquid water and is almost transparent to microwaves.
- The reversing direction of microwave turntables is not a feature designed to encourage uniform heating, as is sometimes believed. In a response to a question in the New York Times, Robert J. Thomas, a professor of electrical engineering, pointed out that the change in direction of rotation occurs because the motors used in microwaves are typically cheap and require a torque to start moving when starting from stationary. The turntable is usually pressed against the load from the last rotation so starts to turn in the opposite direction.
References
M. Vollmer, K. P. Möllmann, & D. Karstädt, More experiments with microwave ovens. Physics Education, vol. 39, no. 4, 2004, pp. 346-351, p. 348.
M. Vollmer, Physics of the microwave oven. Physics Education, vol. 39, no. 1, 2004, pp. 74-81, p.75.
T. K. Ishii, Other microwave Vacuum Devices, In J. C. Whittaker (ed.), The Electronics Handbook, Boca Raton, FL, CRC Press, 1996, 444-457, p. 446.
L. Figura, & A. A. Teixeria, Food Physics: Physical Properties – Measurement and Applications, Berlin, Springer-Verlag, 2010, p. 385.
C. Clairbonre Ray, Micro Go Round, 15th April 2013, New York Times Science Q & A, http://www.nytimes.com/2013/04/16/science/why-does-my-microwaves-turntable-switch-directions.html?_r=0
