A. SoftB. PermanentC. HardD. Brittle
All the other answers sum it up really well. I use a Silent Spinner wheel and it's very quiet. If I'm trying to sleep and it starts to knock around on the side of the cage from aggressive running, I'll take it down for the night, but put it back up immediately when I wake up. For squeaky wheels, olive oil is a safe and effective lubricant.
The only dangers that I know of that a rat faces when it runs on a wheel is injury to its tail and feet. I've never heard of a rat breaking its back when running on a wheel. Though you will want to make sure its big enough and there aren't holes in the surface they run on that are big enough for their toes/feet to get stuck in.
YES!! They can run, but you need to make sure that the wheel is large enough to fit a whole rat. You need to make sure that it will also fit the rat when it is big and fat!! By having a wheel it will make your rats a lot more athletic (which is good so they don't get fat like mine)!! You also have to make sure that the wheel will fit into the cage. You may want to get them treats so that they know that it is Okay! Don't worry Why would they make such big wheels? Hope This Helps )
C. Hard When domain wall is difficult to migrate, magnetization of the ferromagnetic material occurs only when high magnetic field is applied. In other words, this type of ferromagnetic materials are difficult ot magnetize, but once magnetized, it is difficult to demagnetize. These materials are called hard magnetic materials, and are suitable for applications such as permanent magnets and magnetic recording media. Hard magnetic materials have high magnetocrystalline anisotropy. Since large magnetic field is required to demagnetize, their coercivity Hc is usually high, but coercivity is highly sensitive to the microstructurure. www.nims.go.jp/apfim/softhard.ht. Goodbye
