What do you mean by W and u in physics

What do you mean by W and u in physics

This is the Greek alphabet, which is widely used in mathematics and physics
Greek letters are widely used in physics. They can express many physical quantities. For example, the lowercase W and ω are called Omega. They are commonly used to express angular velocity, and the capital form Ω is used to express resistance. The simple use of μ is the dynamic / static friction coefficient, and the constant μ 0 represents vacuum permeability

The physical meaning of R = u divided by I
On Ohm's law

The "definition" formula of conductor resistance
It reflects the "ability of conductor to block current"
The larger the ratio, the greater the ability to block current and the worse the conductivity of conductor
The smaller the ratio, the smaller the ability to block the current and the stronger the conductor's conductive ability