The cooking time for rice in a rice cooker typically ranges from 20 to 30 minutes, depending on the rice cooker's settings and the type of rice being cooked. This duration includes the time it takes for the rice cooker to heat up and the cooking time for the rice itself. For example, a standard 2-cup (uncooked) serving of long-grain white rice usually takes about 20 minutes to cook in a rice cooker, while brown rice may require an additional 10 to 15 minutes due to its higher water content and longer cooking time.

The reason for this varied cooking time lies in the different water absorption rates and cooking requirements of different rice types. White rice, which has been polished to remove the bran and germ, absorbs water more quickly than brown rice, which retains the bran and germ layers. According to the American Rice Producers Association, white rice absorbs about 1.5 to 2 times its weight in water, while brown rice absorbs about 1.75 to 2.25 times its weight in water. This difference in water absorption directly impacts the cooking time needed for each type of rice.

Additionally, the cooking time can be influenced by the rice cooker's specific features. For instance, some rice cookers have a "keep warm" function that maintains the rice at an ideal serving temperature for several hours after cooking. This feature does not add to the cooking time but is important for ensuring the rice remains fresh and warm. Moreover, the capacity of the rice cooker also plays a role; larger cookers may take slightly longer to heat up and cook the rice compared to smaller ones.

In summary, the cooking time for rice in a rice cooker is generally between 20 to 30 minutes, with variations depending on the rice type and the rice cooker's features. Understanding the water absorption rates and cooking requirements of different rice types is crucial for achieving perfect rice every time.