A material that does not easily transmit energy, such as electric current or heat. Materials such as wood, plastic, and ceramics are insulators. Fiberglass is an example of a heat insulator. (Compare conductor.)
An electroencephalogram (EEG) is a noninvasive test that records electrical patterns in your brain. The test is used to help diagnose conditions such as seizures, epilepsy, head injuries, dizziness, headaches, brain tumors and sleeping problems.
An ECG measures electrical activity of the heart. An EEG evaluates electrical impulses of the brain and nerves. An ECG is used to detect heart ailments in patients who have suffered heart attacks or abnormal heart rates. An EEG is a staple test for patients with seizures, tumors, coma or nervous disorders.