Calculate electrical current (Amperes) using Ohm's Law: I = V / R. Essential for electronics, circuit design, and electrical engineering.
⚡ Ohm's Law: I = V / R
Where I = Current (Amperes/A), V = Voltage (Volts/V), R = Resistance (Ohms/Ω)
📊 Calculated Current
0 A
💡 Power (P = V × I)
0 W
I = V ÷ R = 220V ÷ 10Ω = 22 A
📖 What is Electric Current?
Electric current is the flow of electric charge in a circuit. It is measured in Amperes (Amps/A). Current represents how many electrons are flowing through a conductor per second. One Ampere equals one Coulomb of charge passing a point per second.
📐 Ohm's Law Formula for Current
Ohm's Law states that the current through a conductor is directly proportional to the voltage and inversely proportional to the resistance. The formula is:
I = V ÷ R
I = Current (Amperes/A) | V = Voltage (Volts/V) | R = Resistance (Ohms/Ω)
Example 1: V = 220V, R = 10Ω → I = 220 ÷ 10 = 22A Example 2: V = 12V, R = 6Ω → I = 12 ÷ 6 = 2A Example 3: V = 5V, R = 10Ω → I = 5 ÷ 10 = 0.5A
📊 Common Current Values Reference Table
Device / Application
Voltage
Resistance (approx)
Current
LED Light (typical)
5V DC
100-300 Ω
20-50 mA (0.02-0.05A)
USB Charger (phone)
5V DC
2.5-5 Ω
1-2A
Laptop Charger
19V DC
2-4 Ω
3-5A
Car Headlight Bulb
12V DC
2-3 Ω
4-6A
Electric Iron
220V AC
40-55 Ω
4-5.5A
Household Outlet (max)
220V AC
22 Ω
10A (standard circuit)
-saluran
Industrial Motor (small)
220V AC
11 Ω
20A
💡 Applications of Current Calculation
Circuit Design: Determine wire gauge needed for safe current carrying
Battery Selection: Calculate current draw to choose appropriate battery
Fuse Selection: Determine correct fuse rating for protection
Power Supply Sizing: Calculate total current for multiple devices
LED Resistor Calculation: Find correct resistor value for LEDs
Safety Assessment: Ensure wires and components can handle current
🔧 How to Measure Current with a Multimeter
To measure current:
Set multimeter to "A" (Amps) mode (AC or DC as appropriate)
Connect probes in SERIES with the circuit (break the circuit and connect meter between)
Start with highest current range to avoid damaging the meter
Safety note: Never measure current by connecting probes across a voltage source (parallel) - this creates a short circuit!
📝 Frequently Asked Questions (FAQ)
❓ What is the formula for calculating current? ▼
The formula is I = V ÷ R (Current = Voltage divided by Resistance). This is Ohm's Law. For example, if voltage is 220V and resistance is 10Ω, current = 220 ÷ 10 = 22 Amperes.
❓ What is the difference between AC and DC current? ▼
AC (Alternating Current) changes direction periodically (household electricity, 50/60Hz). DC (Direct Current) flows in one direction (batteries, USB power). Ohm's Law applies to both, but AC circuits with inductors/capacitors may need impedance instead of resistance.
❓ How many amps does a typical household outlet provide? ▼
In India, standard household circuits are rated for 10-16 Amperes at 220V. For example, a 10A circuit can handle up to 2200W (10A × 220V = 2200W). Heavy appliances like ACs require 15-20A circuits.
❓ What happens if current is too high for a wire? ▼
Excessive current causes wires to overheat, potentially melting insulation and causing fires. Circuit breakers and fuses are designed to cut off current when it exceeds safe limits. Always use appropriate wire gauge for expected current.
❓ How do I calculate current if I know power and voltage? ▼
You can use the power formula: I = P ÷ V. For example, if a device uses 100W at 220V, current = 100 ÷ 220 = 0.45 Amperes (450mA).
❓ What is a safe current for the human body? ▼
Even small currents can be dangerous. 1-5mA can be felt (tingling), 10-20mA causes muscle contraction, 50-100mA can be fatal. The human body has high resistance (dry skin ~100kΩ, wet skin ~1kΩ), so low voltage (under 50V) is generally safe.
💡 Educational Note: Current is measured in Amperes (Amps/A), named after French physicist André-Marie Ampère (1775-1836). One Ampere equals one Coulomb (6.24 × 10¹⁸ electrons) flowing per second. This calculator uses Ohm's Law for DC and resistive AC circuits.