Basic Electronics Formulas
Basic electronics formulas are the foundation of every circuit you will ever analyse, from Ohm’s Law to power dissipation and divider networks. These calculators let you solve for any unknown by entering the values you already know. Use them for quick bench checks, homework, or sizing components in a new design.
Basic Electronics Formula Calculators
- Ohm's Law V = I × R Current 2 mA, Resistance 1 Ω → Voltage = 2 mV
- Electrical Power P = V × I Voltage 0.33 V, Current 2 mA, Resistance 1 Ω → Power = 0.66 mW
- Voltage Divider Vout = Vin × R2 / (R1 + R2) Input Voltage 0.726 V, R1 (upper) 100 Ω, R2 (lower) 0.22 kΩ → Output Voltage = 0.4991 V
- Current Divider I1 = Itotal × R2 / (R1 + R2) Total Current 4.4 mA, R1 1 Ω, R2 2.2 Ω → Branch Current = 3.025 mA
- Thévenin Equivalent Rth = Voc / Isc Open-Circuit Voltage 0.33 V, Short-Circuit Current 2 mA → Thévenin Resistance = 0.165 kΩ
- Norton Equivalent Rn = Voc / Isc Open-Circuit Voltage 0.33 V, Short-Circuit Current 2 mA → Norton Resistance = 0.165 kΩ
- Temperature Coefficient of Resistance R(T) = Rref × (1 + α × ΔT) Reference Resistance 2.2 Ω, Temp Coefficient (ppm/°C) 0.025, Temperature Change 2.5 °C → Resistance at T = 2.2 Ω
- Kirchhoff's Voltage Law (KVL) ΣV = V₁ + V₂ + V₃ + ... = 0 Voltage Drops 12 V, 26.4 V, 56.4 V → ΣV = 94.8
- Kirchhoff's Current Law (KCL) ΣI = I₁ + I₂ + I₃ + ... = 0 Branch Currents 2 A, 4.4 A, 9.4 A → ΣI = 15.8
- Parallel Plate Capacitor C = ε₀ × εr × A / d Relative Permittivity 0.025, Plate Area 10 mm², Plate Separation 0.1 mm → Capacitance = 0.02214 pF
- Conductance G = 1 / R Resistance 1 Ω → Conductance = 1 S
- Millman’s Theorem (3 Branches) V = Σ(Ei/Ri) / Σ(1/Ri) Source 1 0.726 V, Resistance 1 1 Ω, Source 2 1.55 V, Resistance 2 2.2 Ω, Source 3 155 mV, Resistance 3 4.7 Ω → Node Voltage = 0.8778 V
- Maximum Power Transfer Pmax = Vth² / (4 · Rth) Thévenin Voltage 0.33 V, Thévenin Resistance 1 Ω → Maximum Power = 27.23 mW
- Period from Frequency T = 1 / f Frequency 5 Hz → Period = 0.2 s
Worked result for every Basic Electronics formula
| Formula | Expression | Worked result |
|---|---|---|
| Ohm's Law | V = I × R | Current 2 mA, Resistance 1 Ω → Voltage = 2 mV |
| Electrical Power | P = V × I | Voltage 0.33 V, Current 2 mA, Resistance 1 Ω → Power = 0.66 mW |
| Voltage Divider | Vout = Vin × R2 / (R1 + R2) | Input Voltage 0.726 V, R1 (upper) 100 Ω, R2 (lower) 0.22 kΩ → Output Voltage = 0.4991 V |
| Current Divider | I1 = Itotal × R2 / (R1 + R2) | Total Current 4.4 mA, R1 1 Ω, R2 2.2 Ω → Branch Current = 3.025 mA |
| Thévenin Equivalent | Rth = Voc / Isc | Open-Circuit Voltage 0.33 V, Short-Circuit Current 2 mA → Thévenin Resistance = 0.165 kΩ |
| Norton Equivalent | Rn = Voc / Isc | Open-Circuit Voltage 0.33 V, Short-Circuit Current 2 mA → Norton Resistance = 0.165 kΩ |
| Temperature Coefficient of Resistance | R(T) = Rref × (1 + α × ΔT) | Reference Resistance 2.2 Ω, Temp Coefficient (ppm/°C) 0.025, Temperature Change 2.5 °C → Resistance at T = 2.2 Ω |
| Kirchhoff's Voltage Law (KVL) | ΣV = V₁ + V₂ + V₃ + ... = 0 | Voltage Drops 12 V, 26.4 V, 56.4 V → ΣV = 94.8 |
| Kirchhoff's Current Law (KCL) | ΣI = I₁ + I₂ + I₃ + ... = 0 | Branch Currents 2 A, 4.4 A, 9.4 A → ΣI = 15.8 |
| Parallel Plate Capacitor | C = ε₀ × εr × A / d | Relative Permittivity 0.025, Plate Area 10 mm², Plate Separation 0.1 mm → Capacitance = 0.02214 pF |
| Conductance | G = 1 / R | Resistance 1 Ω → Conductance = 1 S |
| Millman’s Theorem (3 Branches) | V = Σ(Ei/Ri) / Σ(1/Ri) | Source 1 0.726 V, Resistance 1 1 Ω, Source 2 1.55 V, Resistance 2 2.2 Ω, Source 3 155 mV, Resistance 3 4.7 Ω → Node Voltage = 0.8778 V |
| Maximum Power Transfer | Pmax = Vth² / (4 · Rth) | Thévenin Voltage 0.33 V, Thévenin Resistance 1 Ω → Maximum Power = 27.23 mW |
| Period from Frequency | T = 1 / f | Frequency 5 Hz → Period = 0.2 s |
Variables used across Basic Electronics formulas
- V — Voltage in volts (V), the electrical potential difference
- I — Current in amperes (A), the flow of electric charge
- R — Resistance in ohms (Ω), opposition to current flow
- P — Power in watts (W), the rate of energy transfer
- Vin — Input voltage in volts (V)
- R1 — Upper resistor connected to Vin (Ω)
- R2 — Lower resistor connected to ground (Ω)
- Vout — Output voltage taken across R2 (V)
- Itotal — Total current entering the parallel network (A)
- I1 — Current through R1 (A)
- Rth — Thévenin equivalent resistance (Ω)
- Voc — Open-circuit voltage at the terminals (V)
- Isc — Short-circuit current at the terminals (A)
- Rn — Norton equivalent resistance (Ω)
- Rref — Resistance at reference temperature, usually 25°C (Ω)
- α — Temperature coefficient in ppm/°C
- ΔT — Temperature change from reference (°C)
- V₁, V₂, V₃... — Voltages around the loop (V), with sign convention: positive for rises, negative for drops
- I₁, I₂, I₃... — Currents at the node (A), with sign convention: positive for currents entering, negative for currents leaving
- C — Capacitance (F)
- εr — Relative permittivity of the dielectric (dimensionless)
- A — Overlapping plate area (m²)
- d — Distance between plates (m)
- G — Conductance (S)
- E1, E2, E3 — Branch source voltages (V)
- R1, R2, R3 — Branch series resistances (Ω)
- Pmax — Maximum power into the load (W)
- Vth — Thévenin (open-circuit) voltage (V)
- T — Period of one cycle (s)
- f — Frequency (Hz)
Questions people ask about Basic Electronics
- S q e p electrical power — Electrical Power
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