Subject overview
Direct Current
Ohm’s law, electrical power, loaded and unloaded voltage dividers, resistor networks and star–delta conversion.
01 Ohm’s Law & DC Power
Variables
- Uvoltage
- Vvolt
- Icurrent
- Aampere
- Rresistance
- Ωohm
- Ppower
- Wwatt
Key Formulas
For steady-state networks, charge conservation gives Kirchhoff’s current law at each node and energy conservation gives the voltage law around each closed loop. Ohm’s law applies to linear resistors at constant temperature.
Enter any two of U, I, R and P; the two remaining quantities are calculated. Linear positive resistance and nonnegative DC magnitudes. Zero-valued pairs may be underdetermined. Results stay below the fields.
Calculate
Type prefixes directly: 1.5k, 250m or 20u. Results: 3 significant figures.
Enter any two of U, I, R and P; the two remaining quantities are calculated. Linear positive resistance and nonnegative DC magnitudes. Zero-valued pairs may be underdetermined. Results stay below the fields.
Enter the required input values to calculate.
02 Voltage Divider
Variables
- Uininput voltage
- Vvolt
- Uoutoutput voltage
- Vvolt
- U1upper resistor voltage
- Vvolt
- R1upper resistance
- Ωohm
- R2lower resistance
- Ωohm
- Isupply current
- Aampere
- RLload resistance
- Ωohm
- IR2lower resistor current
- Aampere
- ILload current
- Aampere
- Rttotal resistance
- Ωohm
- Rplower parallel resistance
- Ωohm
Key Formulas
For steady-state networks, charge conservation gives Kirchhoff’s current law at each node and energy conservation gives the voltage law around each closed loop. Ohm’s law applies to linear resistors at constant temperature.
Switch between unloaded and loaded operation. With a load, the load resistance is parallel to R₂. Enter independent known quantities; only uniquely determined missing values are calculated.
Calculate
Type prefixes directly: 1.5k, 250m or 20u. Results: 3 significant figures.
Ideal DC divider with positive resistances. Enter the known quantities; uniquely determined missing values appear below. No output load.
Enter the required input values to calculate.
03 Resistors: Series & Parallel
Variables
- R1resistance 1
- Ωohm
- R2resistance 2
- Ωohm
- nnumber of resistors
- 1dimensionless
- Rparallel equivalent resistance
- Ωohm
Key Formulas
For steady-state networks, charge conservation gives Kirchhoff’s current law at each node and energy conservation gives the voltage law around each closed loop. Ohm’s law applies to linear resistors at constant temperature.
Positive ideal resistances R₁ … Rₙ. Switch between series and parallel connection. The next optional field appears automatically; the empty final field is not included.
Calculate
Type prefixes directly: 1.5k, 250m or 20u. Results: 3 significant figures.
Ideal positive resistances. Complete the visible resistances to add the next optional field. The empty final field is not included in the calculation.
Enter the required input values to calculate.
04 Delta–Star Resistance Conversion
Variables
- aresistance a
- Ωohm
- bresistance b
- Ωohm
- cresistance c
- Ωohm
- R1converted resistance 1
- Ωohm
- R2converted resistance 2
- Ωohm
- R3converted resistance 3
- Ωohm
Key Formulas
For steady-state networks, charge conservation gives Kirchhoff’s current law at each node and energy conservation gives the voltage law around each closed loop. Ohm’s law applies to linear resistors at constant temperature.
Switch between delta-to-star and star-to-delta conversion. All three resistances must be positive. The selected direction determines whether a, b and c denote delta branch resistances or star arm resistances.
Calculate
Type prefixes directly: 1.5k, 250m or 20u. Results: 3 significant figures.
Positive linear resistances. Delta inputs a=R₁₂, b=R₂₃, c=R₃₁; star outputs R₁, R₂, R₃.
Enter the required input values to calculate.