Watt Balance Experiment Concepts

Terry Quinn, emeritus director of the International Bureau of Weights and Measures, discusses the redefinition of the kilogram from a physical object to a concept based on physics. He demonstrates the use of a watt balance, which measures weight without relying on the international prototype kilogram. The video explains the principles and equations behind the watt balance, highlighting its reliance on electromagnetic forces and measurements of voltage and velocity. The discussion concludes with the connection of these measurements to the Planck constant, reflecting advancements in modern physics.

What is the main reason for redefining the kilogram?

• To reduce the cost of mass measurements

• To link it to a stable physical constant

• To simplify the measurement process

• To make it more accessible to the public

Why is the international prototype of the kilogram considered unsatisfactory?

• It is too small

• It is difficult to access

• It is not linked to a stable physical constant

• It is too expensive to maintain

What is the primary function of the watt balance?

• To measure electrical resistance

• To measure temperature

• To measure mass without the international prototype

• To measure time intervals

In the first part of the watt balance experiment, what is initially set to zero?

• The micrometer

• The voltage

• The electric current

• The mass

What is the purpose of the Lego motor in the watt balance experiment?

• To measure temperature changes

• To provide a constant magnetic field

• To calibrate the balance

• To move the coil up and down

What two key pieces of information are measured in the second part of the watt balance experiment?

• Voltage and resistance

• Mass and time

• Current and temperature

• Velocity and voltage

What is the downward force on the mass in the watt balance experiment?

• Mass times acceleration due to gravity

• Voltage times resistance

• Current times magnetic field

• Mass times velocity

How is the electromagnetic force in the watt balance expressed?

• Voltage times current

• Current times magnetic field times length

• Mass times acceleration

• Resistance times length

What does the final equation in the watt balance experiment relate?

• Mass and electrical quantities

• Voltage and resistance

• Mass and temperature

• Current and time

What constant is linked to the electrical quantities in modern physics?

• Boltzmann constant

• Planck constant

• Gravitational constant

• Avogadro constant