Understand the relationship
The reasoning behind the result
Nominal field divides potential difference by electrode spacing
E = V/d
V is the potential difference in volts, d is electrode-to-electrode distance and E is nominal electric field. With d in centimetres the result is volts per centimetre; with d in metres it is volts per metre. One V/cm equals 100 V/m.
The gel's physical length and a band's migration distance are different measurements. Substituting either for electrode spacing changes the result. This simple nominal gradient does not reconstruct a nonuniform local field inside a complex tank or buffer geometry.
Current and resistance describe the same stated operating point
V = IR; P = VI = V²/R
I is total current in amperes, R is total cell resistance in ohms and P is electrical power in watts. Milliamperes are divided by 1,000 before multiplication; kilohms are multiplied by 1,000 before division.
If current is supplied, the calculator reports the corresponding V/I resistance. If resistance is supplied, it reports the corresponding V/R current. Resistance depends on the assembled system and conditions and can change with temperature and buffer composition. One operating point does not determine the full run.
Energy requires a time model for power
Q = Pt; 1 Wh = 3,600 J
Q is electrical energy, P is power and t is duration in seconds. The optional energy calculation assumes the displayed power remains constant for the entire entered duration. Watts multiplied by seconds give joules; watts multiplied by hours give watt-hours.
For varying voltage or current, energy instead requires integrating V(t)I(t) over time. Electrical energy is not a predicted buffer temperature: heat capacity, cooling, evaporation, geometry and heat loss are absent from this model.
Electrical arithmetic does not choose a separation protocol
Gel matrix, molecule, buffer, geometry and equipment all affect the appropriate operating conditions and observed migration. A positive numerical result does not establish acceptable separation, compatibility or safe operation.
The potential diagram is an explicitly linear nominal model between electrodes. It does not show a measured voltage profile, band speed, local heating, equipment limits or the location of a gel inside the chamber.
Follow the numbers
Reconcile units before calculating an energy scenario
- An illustrative field of 4 V/cm across 20 cm gives V = 4 × 20 = 80 V.
- A measured 25 mA is 0.025 A, so P = 80 × 0.025 = 2 W and R = 80/0.025 = 3,200 Ω.
- If that power remains constant for 30 minutes, t = 1,800 s and Q = 2 × 1,800 = 3,600 J.
- Equivalently, 30 minutes is 0.5 h, giving 2 × 0.5 = 1 Wh. This is energy, not a temperature rise.
The field, voltage, load and duration reconcile only under their separately stated assumptions.
Quick guide
How to use this calculator
- Choose the missing quantity and matching units. The distance is the separation of the electrodes used to define nominal field.
- Supply the protocol field or measured voltage independently. The examples are arithmetic scenarios, not settings to apply to a gel.
- If current or total cell resistance is known at that voltage, include it to inspect power. Do not substitute a buffer-only or partial resistance.
- Include energy only when explicitly assuming the calculated power remains constant. Actual power can change throughout a run.
Calculation method
Calculation and interpretation
Keep electrode spacing, protocol field and electrical load distinct when checking an electrophoresis setup's arithmetic.
E = V/d; V = Ed; d = V/E; I = V/R; P = VI; Q = Pt when power is held constant.
Worked example
Reconcile units before calculating an energy scenario
The field, voltage, load and duration reconcile only under their separately stated assumptions.
E = V/d; V = Ed; d = V/E; I = V/R; P = VI; Q = Pt when power is held constant.
Supported inputs
Precision and limits
Use independently established settings
No operating voltage, field, cooling requirement or equipment limit is recommended. Follow the applicable validated protocol and equipment instructions. The nominal field does not establish local field uniformity.
No run-time or temperature prediction
Electrical power alone does not determine band speed, separation quality or buffer temperature. Numerical inputs support 10⁻⁹ through 10⁹ in their selected units; explicitly nonnegative positions and times also accept zero. These are calculation limits, not operating recommendations.
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