What requirements should be considered when applying Kirchhoff rules to circuit design?

1. The number of equations to be composed must correspond to the number of unknowns. 2. When composing equations, it is necessary to ensure that each next equation contains at least one unknown quantity that was not included in the previous equations. 3. For each circuit, the direction of its bypass, which determines the signs of the currents and EMF, is chosen arbitrarily. If, as a result of solving the problem, a negative value is obtained for the current strength in some section, then this means that the current in this section goes in the direction opposite to the selected circuit bypass.