Anglais example sentences with "electrodes"

I have never understood correctly what electrodes are.
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An electrolysis is a passage of direct current through an ion-conducting solution, producing a chemical change at the electrodes.
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Then a mild electrical current sent through electrodes on the volunteers’ scalp caused the brain to suppress signals that affect the inner ear.
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Cheok said different tastes are triggered by molecules that cause chemical ionization on the surface of the tongue, sending the brain electrical signals of a specific amplitude and frequency that are possible to reproduce with two electrodes.
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To obtain the sound-stimulated brainwave patterns, Pasley used a device called an electroencephalograph, which measures the electrical firing of the patients' auditory circuits through electrodes already implanted in the patients' brains when they hear spoken words.
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