Parallel resistors do not have the same current flowing through them.
The current through each resistor depends on
- Voltage across its terminals
- Resistance value
Example Current Calculation
For a three resistor network (R1 = 10 Ω, R2 = 20 Ω and R3 = 30 Ω) shown in the picture below the voltage drop across each resistor is the same.
V = V1 = V2 = V3
Assume V = 5 Volt.
The current through each resistor is calculated using Ohm’s law. The calculator below provides the answer in each case by entering the voltage and resistor value.
The current I1, I2, I3 (in Amperes or A) through R1, R2, R3 respectively is:
- I1 = 0.5 A
- I2 = 0.25 A
- I3 = 0.17 A
The current through each resistor is not identical. Instead it is inversely proportional to the impedance. For example, R3 has the largest resistance and therefore the smallest current.
Using Kirchhoff’s Law, The current flowing into node A is the sum of the currents flowing out of the node.
I = I1 + I2 + I3
I = 0.5 + 0.25 + 0.17
I = 0.92 A
Alternatively, this number can also be found using the parallel resistance calculator R = R1 || R2 || R3 = 5.45 Ω.
Using the Ohm’s Law Calculator above with V = 5 V, the current is calculated to be 0.92 A (hence verifying the result).