Iron sheet, dry wood, salt solution, carbon rod, ceramics, human body, glass, wet wood, dry cotton yarn, plastic foam, copper sheet and insulator include: dry wood, ceramics, glass, dry cotton yarn and plastic foam. The specific analysis is as follows:

Substances that are not good at conducting current are called insulators. Insulators are characterized by tight combination of positive and negative charges in molecules, few charged particles that can move freely and high resistivity.

An insulator is a substance that can prevent heat (thermal insulator) or charge (electrical insulator) from flowing. The relative substances of electrical insulators are conductors and semiconductors, which can make charges flow smoothly;

Insulators can be divided into three categories: gaseous (such as hydrogen, oxygen, nitrogen and all non-ionized gases), liquid (such as pure water, oil, coatings and organic acids) and solid (such as glass, ceramics, rubber, paper and aging). Solid insulators are divided into crystalline and amorphous. The actual insulator is not completely nonconductive;

Therefore, among the above substances, insulators include: dry wood, ceramics, glass, dry cotton yarn and plastic foam.

Extended data:

Insulator principle:

Under the influence of some external conditions, such as heating and high voltage, the insulator will be "broken down" and converted into a conductor. Before decomposition, an insulator is not an absolutely nonconductive object. If a voltage is applied to an insulating material, a weak current will appear in the material;

There are usually only a few free electrons in insulating materials, and the charged particles involved in conduction before breakdown are mainly intrinsic ions and impurity particles dissociated by thermal motion. The electrical properties of insulators are reflected in the processes of conductance, polarization, loss and breakdown.

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