# How an electromagnet can calculate kilogram

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#### HarryA

Jan 22, 2017
75
"The new system, now that it's been adopted, will allow anyone with a
Kibble balance to check their weights anytime and anywhere"

Anywhere? There must be more to this balance then they say - does not gravity vary
all over the planet?

see: https://www.bbc.com/news/science-environment-46143399

#### duke37

Jan 9, 2011
5,364
No idea what a Kibble balance is , we used to kibble grain for animals to eat.

The kilogram is a unit of mass, not weight so gravity does not enter into it.

#### Ylli

Jun 19, 2018
373
The kilogram is a unit of mass, not weight so gravity does not enter into it.
The BBC article implies that the force exerted by the 1 kg mass is balanced against the force generated by the electromagnet. But the force exerted by the 1 kg mass is dependent on the gravitational field which it is in.

#### (*steve*)

##### ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd
Moderator
Jan 21, 2010
25,505
A Kiligram is a kilogram in any gravity field (whereas a pound is not).

Kg is a measure of mass, lb is a measure of weight.

The force could be exerted perpendicularly to the gravitational field.

#### HarryA

Jan 22, 2017
75
"In this new application, the balance will be used in the opposite sense; the current in the coils necessary
to support the weight of a standard kilogram mass will be measured, "weighing" the kilogram.
The weight of the kilogram is then used to compute the mass of the kilogram by accurately
determining the local gravitational acceleration."
from: https://en.wikipedia.org/wiki/Kibble_balance

Now one has to determining the local gravitational acceleration.
You will need an apple?

#### duke37

Jan 9, 2011
5,364
Kg is a measure of mass, lb is a measure of weight.
According to Wikipedia the pound is a measure of mass which equal 0.453 592 37kg
I got all tied up in school with trouble understanding the poundal

#### FuZZ1L0G1C

Mar 25, 2014
366
Mass is density per displaced volume, or "lb/ft.sq \ kg/m.sq", and has inertia.
Weight is the gravitational attractive force between two masses.
A mass of "x" would weigh eg 67 kg on terra firma, but only ±23 kg on the lunar surface, and weigh much more on Neptune.
Gravitational force on Earth varies slightly depending on altitude, but the Wiki article mentions that g is measured as part of the calculation process.
I always thought Kilogram and Pound were both masses (or "weight" on a planet), - just a conversion of one unit to another.

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