PartSim Circuit Calculator

Analyze electronic circuits, calculate parameters, and simulate basic circuit behaviors. Essential tool for electronics engineers and students.

Ohm's Law Formula: V = I × R

Where: V = Voltage (Volts), I = Current (Amps), R = Resistance (Ohms)

V
Enter voltage in volts
A
Enter current in amperes
Ω
Enter resistance in ohms

Instructions: Enter any two values to calculate the third. Leave the value you want to calculate empty.

Series Resistance Formula: Rtotal = R1 + R2 + R3 + ...

In a series circuit, the total resistance is the sum of all individual resistances.

Ω
Ω
Ω
Ω
V
Enter source voltage to calculate current and power

Parallel Resistance Formula: 1/Rtotal = 1/R1 + 1/R2 + 1/R3 + ...

In a parallel circuit, the reciprocal of total resistance equals the sum of reciprocals of individual resistances.

Ω
Ω
Ω
Ω
V
Enter source voltage to calculate current and power

Voltage Divider Formula: Vout = Vin × (R2 / (R1 + R2))

A voltage divider produces an output voltage that is a fraction of the input voltage.

V
Ω
Ω
Ω
Enter load resistance to calculate loaded output voltage

Capacitor Charge Formula: Vc(t) = V0 × (1 - e-t/RC)

Where: Vc(t) = Capacitor voltage at time t, V0 = Source voltage, R = Resistance, C = Capacitance

V
Ω
Enter time to calculate capacitor voltage at that time

Inductive Reactance Formula: XL = 2πfL

Where: XL = Inductive reactance (Ω), f = Frequency (Hz), L = Inductance (H)

V
Enter voltage to calculate current through inductor
Calculating circuit parameters...

Circuit Analysis Fundamentals

Circuit analysis is the process of determining the voltages, currents, and power throughout an electrical circuit. Understanding these fundamentals is essential for electronics design and troubleshooting.

Key Circuit Laws:

  • Ohm's Law: V = I × R (Voltage = Current × Resistance)
  • Kirchhoff's Voltage Law (KVL): The sum of voltages around any closed loop is zero
  • Kirchhoff's Current Law (KCL): The sum of currents entering a node equals the sum of currents leaving
  • Power Law: P = V × I = I² × R = V² / R

Circuit Components

Component Symbol Unit Function
Resistor R Ohm (Ω) Limits current flow, divides voltage
Capacitor C Farad (F) Stores electrical energy, blocks DC
Inductor L Henry (H) Stores magnetic energy, opposes AC
Voltage Source V Volt (V) Provides electrical potential difference
Current Source I Ampere (A) Provides constant current flow

Resistor Color Code

Resistors often use color bands to indicate their resistance value and tolerance. Here's how to read them:

Example: 1kΩ ±5% resistor

Brown (1), Black (0), Red (×100), Gold (±5%) = 10 × 100 = 1000Ω = 1kΩ

Color 1st Band 2nd Band Multiplier Tolerance
Black 		0 0 ×1 -
Brown 		1 1 ×10 ±1%
Red 		2 2 ×100 ±2%
Orange 		3 3 ×1k -
Yellow 		4 4 ×10k -
Green 		5 5 ×100k ±0.5%
Blue 		6 6 ×1M ±0.25%
Violet 		7 7 ×10M ±0.1%
Gray 		8 8 ×100M ±0.05%
White 		9 9 ×1G -
Gold 		- - ×0.1 ±5%
Silver 		- - ×0.01 ±10%

Common Circuit Configurations

1

Series Circuits: Components are connected end-to-end, so the same current flows through each component.

2

Parallel Circuits: Components are connected across the same voltage source, so each component receives the same voltage.

3

Voltage Dividers: Two resistors in series create an output voltage that is a fraction of the input voltage.

4

RC Circuits: Resistor-capacitor circuits used for timing, filtering, and signal conditioning.

5

RL Circuits: Resistor-inductor circuits used in filtering and energy storage applications.

Practical Applications

  • Power Supply Design: Voltage regulation and current limiting
  • Signal Conditioning: Filtering, amplification, and impedance matching
  • Timing Circuits: Oscillators, timers, and clock generation
  • Sensor Interfaces: Converting physical measurements to electrical signals
  • Protection Circuits: Overvoltage, overcurrent, and ESD protection

Design Tip: Always consider component tolerances, temperature coefficients, and power ratings when designing circuits. Simulation tools like PartSim can help validate designs before prototyping.

Frequently Asked Questions

In a series circuit, components are connected end-to-end, so the same current flows through all components, but voltage divides among them. In a parallel circuit, components are connected across the same two points, so each component receives the same voltage, but current divides among the branches.

Power (P) in watts can be calculated using several formulas: P = V × I, P = I² × R, or P = V² / R, where V is voltage in volts, I is current in amperes, and R is resistance in ohms. Always ensure components are rated for the calculated power to prevent overheating and failure.

The time constant (τ, tau) of an RC circuit is τ = R × C, where R is resistance in ohms and C is capacitance in farads. It represents the time required for the capacitor to charge to approximately 63.2% of the source voltage or discharge to 36.8% of its initial voltage. After 5 time constants, the capacitor is considered fully charged or discharged.

Reactance is the opposition to alternating current (AC) offered by capacitors and inductors, while resistance is the opposition to both direct current (DC) and AC offered by resistors. Unlike resistance, which dissipates energy as heat, reactance stores and releases energy. Capacitive reactance (XC) decreases with increasing frequency, while inductive reactance (XL) increases with frequency.

To choose the right resistor wattage, calculate the power dissipation using P = I² × R or P = V² / R. Select a resistor with a power rating at least 1.5 to 2 times the calculated value to provide a safety margin. For example, if a resistor will dissipate 0.5W, use at least a 1W resistor. Also consider ambient temperature, as derating may be necessary in high-temperature environments.