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Ohm's Law and Power Calculator

Enter any two values to calculate the others:

1. What is an Ohm's Law and Power Calculator?

Definition: This calculator uses Ohm's Law and power equations to compute power (P), current (I), voltage (V), and resistance (R) in a DC or single-phase AC circuit, given any two known values.

Purpose: It is used in electrical engineering and electronics to design circuits, select components, and analyze circuit behavior.

2. How Does the Calculator Work?

The calculator applies Ohm's Law and power formulas:

Ohm's Law: \( V = I \cdot R \), \( I = \frac{V}{R} \), \( R = \frac{V}{I} \)
Power: \( P = V \cdot I \), \( P = I^2 \cdot R \), \( P = \frac{V^2}{R} \)

Where:

  • \( P \) is power (watts)
  • \( I \) is current (amps)
  • \( V \) is voltage (volts)
  • \( R \) is resistance (ohms)

Steps:

  • Enter any two values (e.g., voltage and current) and select their units (e.g., V, mA)
  • Convert inputs to base units (W, A, V, Ω)
  • Calculate the remaining two values using the appropriate formulas
  • Convert results back to the selected units
Display format:
  • If the result is > 10000 or < 0.0001 (and not zero), use scientific notation (e.g., \( 1.23456e-3 \))
  • Otherwise, display with 5 decimal places

3. Importance of Ohm's Law Calculations

Details: These calculations are fundamental for designing safe and efficient electrical circuits, ensuring proper component ratings, and preventing overloads or failures in electronics and power systems.

4. Using the Calculator

Tips: Enter exactly two positive values. Select appropriate units (e.g., mA for small currents, kV for high voltages). The calculator handles unit conversions automatically. For AC circuits, use RMS values for voltage and current.

Examples:

  • Voltage and Current: \( V = 12 \, \text{V} \), \( I = 2 \, \text{A} \):
    • \( P = 12 \cdot 2 = 24 \, \text{W} \)
    • \( R = \frac{12}{2} = 6 \, \text{Ω} \)
  • Power and Resistance: \( P = 100 \, \text{W} \), \( R = 50 \, \text{Ω} \):
    • \( V = \sqrt{100 \cdot 50} = 70.71068 \, \text{V} \)
    • \( I = \frac{70.71068}{50} = 1.41421 \, \text{A} \)
  • Voltage and Resistance: \( V = 230 \, \text{V} \), \( R = 1000 \, \text{Ω} \):
    • \( I = \frac{230}{1000} = 0.23 \, \text{A} = 230 \, \text{mA} \)
    • \( P = 230 \cdot 0.23 = 52.9 \, \text{W} \)

5. Common Conversion Table

The following table provides quick reference calculations for common voltage and current values:

Voltage (V) Current (A) Power (W) Resistance (Ω)
5 0.5 2.5 10
12 2 24 6
230 0.23 52.9 1000
110 5 550 22

Use this table for quick lookups or to verify calculator results.

6. Frequently Asked Questions (FAQ)

Q: What is Ohm's Law?
A: Ohm's Law states that the current through a conductor is directly proportional to the voltage across it, with resistance as the constant of proportionality (\( V = I \cdot R \)).

Q: Can this calculator be used for AC circuits?
A: Yes, for single-phase AC circuits, use RMS values for voltage and current. It does not account for power factor or three-phase systems.

Q: Why do I need to enter exactly two values?
A: The equations require two known variables to solve for the other two uniquely. Entering more or fewer values leads to ambiguous or impossible solutions.

Q: What happens if I enter negative values?
A: Negative values are invalid for these calculations, as power, current, voltage, and resistance are positive quantities in this context.

Q: How are units handled?
A: The calculator converts inputs to base units (W, A, V, Ω) for calculations and converts results back to the selected units, ensuring flexibility for various scales (e.g., mA for small currents, kV for high voltages).

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