# Formula: 3. Maxwell equation (integral form) Electric field (E field)    Magnetic flux density (B-field)

## Electric field

Unit
Electric field indicates how large and in what direction the electric force on a charge would be if that charge were placed at location $$(x,y,z)$$.

In the third Maxwell equation in integral form, on the left-hand side is the line integral of the electric field, which corresponds to the voltage along the line $$L$$.

## Magnetic field

Unit
Magnetic flux density determines the force on a moving electric charge.

On the right-hand side of the third Maxwell's equation is the negative temporal change of the magnetic flux. Minus sign accounts for the Lenz rule. The third Maxwell equation means that a magnetic field changing in time causes an electric voltage and vice versa.

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