Answer to Question #86364 in Electric Circuits for PAUL

Question

Define the following physical quantities and their SI unit:
Electric current
Terminal voltage
Resistance
Explain the term Root mean square (rms)of the voltage. How do we obtained rms from
the voltage peak value?

Answer 1

Electric current is a flow of electric charge.

The SI unit of electric current is the ampere, which is the flow of electric charge across a surface at the rate of one coulomb per second.

Terminal voltage is the voltage / potential difference across the terminals of a cell or a battery. Voltage a.k.a. electric potential difference, electric pressure or electric tension is the difference in electric potential between two points.

In the International System of Units, the derived unit for voltage is named volt. In SI units, work per unit charge is expressed as joules per coulomb, where 1 volt = 1 joule (of work) per 1 coulomb (of charge). The official SI definition for volt uses power and current, where 1 volt = 1 watt (of power) per 1 ampere (of current).

Electrical resistance of an object is a measure of its opposition to the flow of electric current.

The SI unit of electrical resistance is the ohm (Ω).

The RMS voltage is the square Root of the Mean over one cycle of the Square of the instantaneous voltage. It is a concept that has to do with alternating current (AC).

How RMS voltage relates to the peak voltage, depends on the waveform of the AC. For the common case of sinusoidal voltage, $V_{rms} = \frac{1}{\sqrt{2}}V_{pk}.$

Sources and more information:

https://en.wikipedia.org/wiki/Electric_current

https://en.wikipedia.org/wiki/Voltage

https://en.wikipedia.org/wiki/Electrical_resistance_and_conductance

https://en.wikipedia.org/wiki/Alternating_current#Root_mean_square_voltage