Final answer:
To confirm Kirchhoff's junction rule, currents must be measured at points just before and after the junction, and at each branch around the junction, ensuring that the sum entering equals the sum leaving.
Step-by-step explanation:
The three criteria that a variable kVp scale must meet to directly confirm Kirchhoff's junction rule are:
- The sum of currents entering a junction must equal the sum of currents leaving the junction.
- Current measurements should be taken at points just before the junction, just after the junction, and at each branch leading into or out of the junction.
- Current must be consistently measured in terms of direction, either entering or leaving the junction, to ensure the sums can be accurately compared.
By measuring the currents at these critical points, the compliance with Kirchhoff's junction rule can be validated, which states that the total current entering a junction in an electrical circuit must be equal to the total current leaving that junction.