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.