Ohm's Law Calculator
Find any of V, I, or R given two values
When to Use Which Form
• V = IR → when you know current and resistance
• I = V/R → when you know voltage and resistance
• R = V/I → when you know voltage and current (finding unknown R)
• V = IR → when you know current and resistance
• I = V/R → when you know voltage and resistance
• R = V/I → when you know voltage and current (finding unknown R)
Quick Reference
| Known | Find | Formula |
|---|---|---|
| V, I | R | R = V/I |
| V, R | I | I = V/R |
| I, R | V | V = IR |
Thinking Step
Enter any 2 values, leave the third blank. The calculator finds the missing one. If all 3 are filled, it verifies consistency of V = IR.
Series Resistance
Enter values separated by commas (e.g., 10, 20, 30)
Enter values above and calculate
Formula: R_s = R₁ + R₂ + R₃ + ...
Parallel Resistance
Enter values separated by commas (e.g., 10, 20, 30)
Enter values above and calculate
Formula: 1/R_p = 1/R₁ + 1/R₂ + ...
Wire Resistance Calculator
Enter ρ, L, A above
Wire Resistance Trap in JEE
If wire is stretched to double its length: A halves (volume preserved → L×A = constant). So R = ρL/A becomes ρ(2L)/(A/2) = 4R. Resistance becomes 4 times. If stretched to n times: R becomes n² times. This comes in JEE Main almost every alternate year.
⚡ Power & Heat Calculator
Enter at least 2 of {V, I, R}
Bulb Comparison Tool
Enter ratings and click compare
The Bulb Problem Trap
Series: Lower watt (higher R) bulb glows brighter. P=I²R, I same → higher R = more power.
Parallel: Higher watt (lower R) bulb glows brighter. P=V²/R, V same → lower R = more power.
Parallel: Higher watt (lower R) bulb glows brighter. P=V²/R, V same → lower R = more power.
🔋 EMF & Terminal Voltage
Enter ε, r, R to calculate
Mixed Cell Grid Calculator (m × n)
Enter values above
Maximum Current Condition
For maximum current from a mixed grid: External R must equal effective internal resistance (R = nr/m). The optimal ratio m/n = √(r/R). This is a classic JEE optimization problem.
⚖ Wheatstone Bridge Checker
Enter the four arm resistances. The tool checks if the bridge is balanced (P/Q = R/S) and finds the unknown S if needed.
Enter all four arm resistances
Bridge Diagram
A (+)
P
B ← G → D
Q
R
C (−)
S (unknown)
Balance: P/Q = R/S | No current in galvanometer G
Meter Bridge Calculator
📏 Potentiometer — EMF Comparison
Enter ε₁, l₁, l₂ to find ε₂
Internal Resistance Finder
Enter R, l₁, l₂ to find r
Potentiometer Accuracy Tip
Potentiometer gives accurate results because at balance, NO current is drawn from the cell being measured. A voltmeter draws current and gives a slightly lower reading (terminal voltage, not EMF). This distinction scores in both CBSE and NEET.
Circuit Diagram Generator
Yellow = resistors | Green = battery/EMF source