Calculator
Example Data Table
| Total Current | R1 | R2 | R3 | Expected Largest Branch |
|---|---|---|---|---|
| 10 mA | 100 Ω | 220 Ω | 470 Ω | R1 |
| 2 A | 4 Ω | 8 Ω | 16 Ω | R1 |
| 24 V mode | 120 Ω | 240 Ω | 360 Ω | R1 |
Formula Used
For parallel resistors, conductance is:
Gn = 1 / Rn
Total conductance is:
GT = G1 + G2 + G3 + ...
Equivalent resistance is:
Req = 1 / GT
Branch current is:
In = IT × Gn / GT
For two resistors, current through R1 can also be written as:
I1 = IT × R2 / (R1 + R2)
Power in each branch is:
Pn = In2 × Rn
How to Use This Calculator
- Select whether you know total current or parallel voltage.
- Enter the source value and matching unit.
- Choose the resistance unit used by all branches.
- Enter at least two parallel resistor values.
- Add optional branch labels for clearer reports.
- Choose output units and decimal places.
- Press Calculate to view the result above the form.
- Use CSV or PDF download for saved results.
Current Divider Rule Article
Why Current Divides
A current divider rule calculator helps you study parallel circuits. It shows how input current separates between branches. Each branch receives a share based on its conductance. A lower resistance has higher conductance. So it carries more current. A higher resistance carries less current.
Practical Circuit Value
This tool is useful when a circuit has many parallel resistors. Manual work can become slow. One small mistake can change every result. The calculator lists each branch current, voltage, power, and percentage share. It also gives total conductance and equivalent resistance. These values help you check design safety.
How the Rule Works
The rule works because all parallel branches share the same voltage. The supply current equals the sum of branch currents. Conductance is the inverse of resistance. The branch conductance is compared with total conductance. That ratio gives the current share. This method works for two branches and larger branch groups.
Using Units Correctly
Use realistic units before making decisions. Enter milliamps when the source is small. Enter amps when the source is large. Match all resistor values to the same unit. The calculator converts the selected unit internally. This keeps the table consistent. It also reduces repeated conversion work.
Power and Heat Checks
Power is included for practical checking. A branch can have a safe current but unsafe heat. Power equals current squared times resistance. Compare that value with the rated resistor wattage. Use a higher rating when heat margin is small. Good design usually leaves extra room.
Exports and Comparison
The CSV export helps with spreadsheets. The PDF export helps with reports. You can save the result table after every calculation. This makes comparisons easier. It is useful when testing several branch networks. Change one resistor and calculate again. Then compare current share changes.
Important Limits
This calculator is a learning aid. It does not replace circuit testing. Real parts have tolerance, temperature drift, and wiring resistance. High frequency circuits also add capacitance and inductance. For precision work, measure the assembled circuit. For high power work, follow safety rules and datasheets.
Learning Benefits
It also helps teachers build examples. Students can change one branch at a time. They can see the rule react instantly. Technicians can estimate loads before measuring. Designers can review current balance during early planning. These quick checks support better circuit judgment. Keep notes for each case.
FAQs
What is the current divider rule?
It is a method for finding branch current in a parallel circuit. Current divides according to branch conductance. Lower resistance usually receives more current.
Can this calculator handle more than two branches?
Yes. Enter two or more resistor values. The calculator uses conductance ratios, so it works for many parallel branches.
Why does the lowest resistance get the most current?
Lower resistance gives higher conductance. In a parallel network, each branch has the same voltage. More conductance allows more current to flow.
What units should I enter?
Use one resistance unit for every branch. Then choose the matching unit in the form. The calculator converts values internally.
Can I calculate branch current from voltage?
Yes. Select parallel network voltage as the known source type. The calculator finds each branch current using voltage divided by resistance.
What does equivalent resistance mean?
Equivalent resistance is the single resistance that could replace all parallel branches. It gives the same total current at the same voltage.
Why is power shown?
Power helps you check heat and resistor rating. A branch may have acceptable current but still need a higher wattage rating.
Are the CSV and PDF files exact records?
They store the calculated values from your submitted inputs. Use them for reports, worksheets, design notes, and comparison records.