Alternating Current

Alternating current (AC) is an electric current that periodically changes direction and usually varies in magnitude, making it fundamental to modern electrical systems and the study of electricity and magnetism. A changing voltage drives charge back and forth through a circuit, often producing a sinusoidal waveform described by its frequency, amplitude, phase, and root-mean-square value; electromagnetic induction enables transformers to raise or lower the voltage. AC principles support efficient power generation, transmission, and distribution, while circuit analysis of resistance, capacitance, and inductance predicts phase relationships and energy transfer. These concepts underpin household electricity, motors, communication systems, and power-grid design.

Alternating Current - Related Videos

Research

JoVE Journal - Neuroscience

The Combination of Transcranial Alternating Current Stimulation and Electroencephalogram

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2025

This protocol establishes a practical approach for combining HD-tACS with EEG to examine stimulation effects on neural oscillations during cognitive tasks, using theta-frequency stimulation in working memory as an exemplar.

Research

JoVE Journal - Behavior
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Concurrent Electroencephalography Recording During Transcranial Alternating Current Stimulation (tACS)

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Cited by 29 •

2016

In this article we explain how to set up a concurrent transcranial alternating current stimulation and EEG experiment.

Research

JoVE Journal - Behavior
Free Sample

Simultaneous Transcranial Alternating Current Stimulation and Functional Magnetic Resonance Imaging

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Cited by 18 •

2017

Transcranial alternating current stimulation (tACS) is a promising tool for noninvasive investigation of brain oscillations, though its effects are not completely understood. This article describes a safe and reliable setup for applying tACS simultaneously with functional magnetic resonance imaging, which can increase understanding oscillatory brain function and effects of tACS.

Establishing Concurrent Transcranial Alternating Current Stimulation and Electroencephalography for Recording Human Brain Activity

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2025

Source: Fehér, K. D. et. al., Concurrent Electroencephalography Recording During Transcranial Alternating Current Stimulation (tACS). J. Vis. Exp. (2016)This video demonstrates the setup of concurrent transcranial alternating current stimulation (tACS) and electroencephalography (EEG) experiments to deliver rhythmic electrical signals to the brain while recording brain activity. The procedure ensures electrode isolation and prevents gel bridging for accurate stimulation and clean EEG signals.

Effects of Transcranial Alternating Current Stimulation on the Primary Motor Cortex by Online Combined Approach with Transcranial Magnetic Stimulation

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Cited by 11 •

2017

Transcranial Alternating Current Stimulation (tACS) allows the modulation of cortical excitability in a frequency-specific fashion. Here we show a unique approach which combines online tACS with single pulse Transcranial Magnetic Stimulation (TMS) in order to "probe" cortical excitability by means of Motor Evoked Potentials.

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