The law of energy conservation says that energy does not disappear anywhere. It only changes one view of another, keeping the quantity. The law is fair also for electrical circuits therefore the energy given by sources is equal to the energy consumed in resistive resistance. From here equality of expressions of capacities of sources and capacities in resistance which is called the equation of balance of capacities follows. Drawing up this equation the important task allowing to check correctness of calculations of currents and tension in an electrical circuit
Instruction
1. Determine capacities of all sources of an electrical circuit. The power given by sources of tension of Rhee = to EI where E – the operating EMF value of a source, and I – the value of current proceeding through this source.
2. Find the algebraic sum of the capacities given by sources. If the valid (positive) direction of current through a source coincides with the EMF direction, then the power of such source positive. If the direction of current through a source to an opposite direction the EMF, then power of such source negative. For finding of the algebraic sum of capacities, put positive capacities and from the received sum take away all negative capacities of sources.
3. Determine capacities in resistive resistance. Power in the resistive resistance of Rn = (I^2)*R, where I – current in the resistor, R – its resistance. Power in the resistor always is positive as the power spent for heating does not depend on the direction of current.
4. Find the arithmetic sum of the capacities disseminated in resistive resistance of a chain. For finding of this sum put the found values of the capacities consumed on each resistor.
5. Compare the sum of the capacities given by sources with the sum of the capacities consumed by resistance. If the electric circuit is calculated correctly, both values of the received sums will be equal among themselves. The balance condition is satisfied. The received equality – the equation of balance of capacities for the set electric circuit.