# Questions tagged [si-units]

A set of internationally accepted units to aid in communication of measurements.

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### Does dimensional consistency imply the same units?

Can two units having the same dimensions always be used interchangeably? For example $s^{-1}$ and $\frac{rad}{s}$ have the same physical dimension, does that mean we can measure frequency $\nu$ with ...
1 vote
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### Is Joule equivalent to Joule/radian? [duplicate]

The work a constant torque does when it moves a particle through an angel $\theta$ is given by $\tau \theta$. The work is measured in Joule, so the torque should be measured Joule/radian, but the ...
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### Definition of an electron volt

One electron volt is defined as the kinetic energy of a electron in a potential of $1$ volt. Hence, by conservation of energy, electric potential energy = kinetic energy: $$q V = \mathrm{K.E.}$$ As ...
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### Electric field definition

In my book it says that "electric field" is defined as the "force per unit charge". What does the "unit charge" mean? My initial thoughts was that it meant 1 Coulumb, but ...
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### Why are the seconds/minutes/hours units are universally used, while other measures have several units? [closed]

There are several units to measure length like meter, foot, and rod. The same is true for weight. While time seem to have a universal unit which is the second. Was there other measures of time that ...
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### Does gravity change local space and time units?

Gravity is the curvature of spacetime. Therefore, gravity affects spatial and temporal dimensions in some parts of space. We know that measuring the speed of light in the observer's local inertial ...
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### What does stand behind the formula: "watt = ampere * volt"?

I know the "watt = ampere * volt" formula, but I don't understand what it means. So, let's start from the beginning. Coulomb answers the question: how many electrons do you have (in a ...
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### Why the specific factor of $2 * 10^{-7}$ is used while defining 1 ampere?
while defining an ampere through force between two current-carrying wires, I noticed that they considered the force between two wires as $2 \times 10^{-7}$ forming a definition as follows:- "One ...