when the beaker has rated capacity of 10 ml, does it mean that it has to be filled to the brim?
No. Chemical beakers usually have an etched line in the glass where the liquid level is supposed to be when "full"
I didn't know that. I guess I always used "backward" beakers. Isn't technology great?
I answered based upon what I remember from college and high school chemistry. That was over 50 years ago. Apparently I was wrong.
There are such things as calibrated beakers. Some are shown at
http://www.alibaba.com/product-gs/51612146/glass_beaker.html
For info on the "rated capacity" of a beaker, see
http://www.apug.org/forums/forum37/6186-beaker-design.html
No, you probably are not wrong and I didn't doubt you. Your schools may have had the money to buy those calibrated beakers and mine didn't. Those calibrated beakers really are quite nice.
When a beaker has a rated capacity of 10 ml, it means that its maximum volume is 10 ml. However, it does not necessarily have to be filled to the brim. The rated capacity indicates the maximum volume that the beaker can hold, but you have the flexibility to use it to the desired level, as long as it does not exceed its rated capacity.
To determine the exact volume you want to measure, you can use a measuring tool such as a graduated cylinder or a pipette. These tools have markings at different increments (milliliters, in this case) to help you measure a specific volume accurately. By using a measuring tool, you can ensure that you are not exceeding the beaker's rated capacity and have control over the amount of liquid you want to measure or contain.