# What is Direct Current Circuit Analysis?

In this tutorial, we are going to learn about What is Direct Current Circuit Analysis?

Foundation of DC circuit operation-

• In the analysis of many electronic circuits, both direct and alternating current/voltages exist. In seeking out faulty components for repair, circuits can be viewed based on the affects of direct or alternating current and voltage changes based on circuit components.  The DC voltage levels may vary based on the added voltages and current from the additional AC potentials. In circuit operations. For repair purposes, DC voltages will provide a good indication of what is going on inside the circuits with its devices. An average based on normal conditions.
• Direct current circuits have a steady constant voltage applied to resistive/inductive/capacitive loads.  The voltage source can be a single power source or multiple supply sources. Direct current circuits form the basis of most electronics circuits. In many circuits an AC voltage in added to the DC voltages, in others circuits DC voltages are switched on and off to produce a carrying level of DC voltage.
• Two circuits devices commonly used in electronic circuit are the Inductor and Capacitor. A resistor is a circuit component used to restrict the flow of current. Inductors and capacitors are used to store energy. Inductors consist of coils of wire that develop magnetic energy with current flow, and capacitors are insulation material that will hold current in an electrostatic field.
• DC current will travel through Inductor devices; in capacitor devices, the DC current will store resulting in stores electrostatic field that will eventually stop the flow of DC currents. Within the inductors, a DC voltage can develop a strong magnetic field that can pull or push, while in a capacitor the DC current will create joules of stored energy with an associated energy reverse electrostatic field. The magnetic field of DC currents and voltages in an capacitor, this allow sharing of the stored energy.
• Analysis of resulting currents and voltages that are developed by complaining AC and DC sources can be hard to calculate. In DC analysis, you calculate the resulting static voltages and currents of single and multiple DC power sources. The addition of AC power sources to DC voltages and current will cause changes to circuit levels. Understanding DC condition of an electronic circuit is critical to finding faults any large voltage or current change found within a circuit normally result in changes to the DC condition of the circuit rather than the addition of a potential.
• AC faults can cause major problems, but in most cases, AC problems will result in different types of circuit’s faults than DC changes to circuits operations. AC problems can result in distortion to signal such a sound or video image, changes in timing of circuit events, or at times over heating of components. DC circuit problem can cause dead circuit operations, no signal passage through a circuit, or blown fuses. These rules do not always hold true but provides a good starting point to look for problems.

Ohm’s law within DC circuits

Voltage = Current*Resistance                          Voltage – Measured in volts = E or V

Current = Voltage/Resistance                          Current – Measured in Amperes – I

Resistance – Voltage/ Current                         Resistance measured in Ohms – R

Conductance – 1 / Resistance                         Conduction measured in Siemens – G

The Ohm’s wheels can be helpful in remembering these formulas.

Series and Parallel DC Circuit Operations – Calculation and Design.

Within DC circuit, device can be interconnected in either as a series or parallel wiring arrangement. A circuit must have power source, a conductive path exists to carry current throughout the circuit. A parallel circuit has multiple paths for current each device is connected across the power source.

Example of a series circuit with a resistive load-

B1 is the DC power source

SW1 is the power switch

R1 is a 1K-ohm resistive load

R2 is a 2K – ohm resistive load

Ohm’s Law for a series circuit-

Voltage total is 24V – the total source potential felt by the circuit, to force a common current through all load require more voltage pressure for larger resistance and lower amount of force for smaller loads. The total source voltage must be divided between each load.

VT = V1+V2 in this circuit R1 resistance is ½ of the resistance of R2. It should take half the force of the voltage to push a common current through R1. In this circuit, the drop of voltage across R1 is 16 volts and the drop across R2 is 8 volts. The additional of each is 24 volts – the source potential.

IT = I1 or I2 finding current level in series circuit requires knowledge of various circuit parameters such as voltage drop or total circuit resistance. These values could be mathematically calculated or measured within a functional circuit. To use Ohm’s law to calculate total circuit current you would divide the source voltage from the resistance felt by the source –IT = VT/ RT, IT = 24V/3 K  ohm = 8mA, current through R1 and R2 would  equal the total voltage of 8mA. There is only one conductive path for current so the total current flows through all loads.

PT – Total power will always equal the energy consumed by each load, PT = P1+P2 . The total power that is consumed is a result of power lost from the source. For a circuit to continue its operations it must have a renewable source of energy. Batters must be recharged to make up for the loss of energy. Power supplies must be connected to power source such as a power outlet or the loss of energy. Power is equal to current through the device times its voltage drop or the voltage drop divided by resistance of the load. In direct the load and source use the supply energy in phase, so true power will equal apparent power. In circuits that consume alternating  current, calculation of real power used can be a more complex process.