Parallel Circuits
Parallel branches share the same voltage.
About this topic
In a parallel circuit, components are connected across the same two points on separate branches. Each branch has the same voltage, the currents add up to the total, and the total resistance follows 1/R = 1/R₁ + 1/R₂ + …, always smaller than the smallest branch.
For example, two 6 ohm resistors in parallel give 1/R = 1/6 + 1/6, so R = 3 ohms. On a 12 V supply each branch carries 2 A, for a total of 4 A. Adding a branch gives the current an extra path, so total resistance falls.
If one branch fails the others keep working, which is why household sockets and lights are wired in parallel. Adding more branches draws more current from the supply, and plugging too many appliances into one extension lead can overheat it.
Many students expect that adding resistors always raises resistance, which is true only in series. In parallel the total drops, and each branch behaves independently of the others, so a bulb in one branch does not dim when another is added.
Key ideas
- Currents add
- 1/R = 1/R₁ + 1/R₂
- One failure doesn't stop the rest
Quick check
Use cases: where Parallel Circuits helps
- Homework: review the key idea behind Parallel Circuits before you start a problem set.
- Exam revision: use the quick check to test whether you can recall Parallel Circuits without notes.
- Visual learning: play with the interactive lab to see how Parallel Circuits changes when you adjust its inputs.
- Teaching a friend: explain Parallel Circuits in your own words, then compare your version with the key ideas.
The same laws describe car crashes, sports, satellites and everyday machines.
Frequently asked questions
What is Parallel Circuits?
Parallel branches share the same voltage.
What will I learn in Parallel Circuits?
Currents add. 1/R = 1/R₁ + 1/R₂. One failure doesn't stop the rest.
Is Parallel Circuits part of Physics?
Yes. It is one of 150 Physics topics on LearnViz HighSchoolEdu, with 3 key ideas, a live animation and a quick check.
Does the Parallel Circuits lab work on a phone or tablet?
Yes. The animation resizes to fit your screen and supports touch, so you can drag, tap and slide with your finger.
How should I study Parallel Circuits?
Read the summary and key ideas first, play with the interactive lab to see the idea in motion, then answer the quick check. If you get a question wrong, go back to the key idea it tests.
Do I need an account, and is my progress saved?
No account is needed. Marking a topic as learned is saved in your own browser, so it stays on that device and is not sent to a server.