Kirchhoff's current law and Kirchhoff's voltage law are introduced

Kirchhoff's current law and Kirchhoff's voltage law are introduced

Kirchhoff's current law (KCl): in a lumped circuit, the algebraic sum of branch currents of all outgoing nodes is equal to zero for any node at any time
Kirchhoff's law of voltage (KVL): in a lumped circuit, the algebraic sum of all branch voltages along any circuit at any time is equal to zero

Ask a question about Kirchhoff's law of voltage
In a dual power supply circuit, the two resistors are 8 ohm and 10 ohm respectively. The EMF directions of the two power supplies are opposite, 20 V and 10 V respectively. If the internal resistance is 1 ohm, what are the voltages on the two resistors
The resistance and power supply are all connected in series

If the circuit is a series circuit, the sum of circuit voltage is zero and the current is equal
So: (8 + 10 + 1 + 1) * current = (20-10)
So: current = 0.5
Therefore: the voltages of 8 and 10 are 4V and 5V respectively
In case of parallel connection: total resistance = 1 / [0.5 + 1 / (1 / 8 + 1 / 10)]
Total voltage = 10V;
Total current = 10 / (89 / 18) = 2.02 (approximate)
So: internal voltage = 2.02 * 0.5 = 1.01v;
So the voltage above 8 and 10 is 10-1.01 = 8.99v;

Contents of Kirchhoff current law

For any node or closed surface in any lumped parameter circuit, at any time, the algebraic sum of all branch currents passing through the node or closed surface is equal to zero. That is to say, for any node, ∑ I = 0