Electronics Basics: Follow Parallel Branches

Distinguish shared voltage from divided current.

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Parallel resistors connect across the same pair of nodes, so they share a voltage. Branch currents add to the total source current. Use ideal steady DC with a 6 V source across a 300-ohm branch and a 600-ohm branch. Use diagrams and calculations only. Never use wall outlets, short batteries, open powered equipment or handle charged capacitors.

Worked example

The branch currents are 6/300 = 0.02 A and 6/600 = 0.01 A. Their sum is 0.03 A. Equivalent resistance is 6/0.03 = 200 ohms, less than either branch resistance.

A six-volt ideal source connects across two parallel branches. The 300-ohm branch carries 20 milliamps and the 600-ohm branch carries 10 milliamps; source current is 30 milliamps.

Would you believe it?

Adding a resistor in parallel provides another path and lowers the equivalent resistance. The way parts connect matters, not just their individual values.

OpenStax: series and parallel circuits

Question 1 What voltage is across each branch? 6 V 3 V 12 V

Question 2 What current flows in the 300-ohm branch? 10 mA 30 mA 20 mA

Question 3 What current flows in the 600-ohm branch? 60 mA 10 mA 20 mA

Question 4 What is the total source current? 30 mA 10 mA 200 mA

Question 5 What is the equivalent resistance? 900 ohms 450 ohms 200 ohms

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