Circuit

Electricity
definition

Also known as: electric circuit, closed circuit

Grade 3-5

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An electrical circuit is a closed path through which electric current flows from a power source, through components, and back to the source. Every electrical device depends on circuits, from the simplest flashlight to the most complex computer.

Definition

An electrical circuit is a closed path through which electric current flows from a power source, through components, and back to the source.

💡 Intuition

A circuit is a complete loop — like a circular track that electrons run around. Break the loop and everything stops.

🎯 Core Idea

Current only flows when the circuit is complete — a break anywhere stops the entire flow.

Example

A flashlight: battery (source) + switch + bulb (load) + wires, all forming a complete loop.

Notation

I is the current in amperes (A), V is the voltage of the source in volts (V), and R is the total resistance of the circuit in ohms (\Omega). A closed loop satisfies Kirchhoff's voltage law: \sum V = 0 around any loop.

🌟 Why It Matters

Every electrical device depends on circuits, from the simplest flashlight to the most complex computer.

💭 Hint When Stuck

When analysing a circuit, first trace the path from the positive terminal of the power source through each component and back to the negative terminal. Check whether the loop is complete — if there is any break, no current flows. Then identify whether components are in series (one path) or parallel (branching paths).

Formal View

An electric circuit is a closed conducting path that allows charge to flow continuously. By Kirchhoff's current law, the total current entering any junction equals the total current leaving it: \sum I_{\text{in}} = \sum I_{\text{out}}.

🚧 Common Stuck Point

A switch works by physically breaking the circuit (open = off, closed = on).

⚠️ Common Mistakes

  • Thinking current gets 'used up' as it passes through components — current is the same entering and leaving a component; it is energy that is transferred.
  • Confusing an open circuit (switch off, no current) with a short circuit (zero-resistance path that causes dangerously high current).
  • Forgetting that every working circuit needs a complete loop — even one loose wire stops all current flow.

Frequently Asked Questions

What is Circuit in Physics?

An electrical circuit is a closed path through which electric current flows from a power source, through components, and back to the source.

When do you use Circuit?

When analysing a circuit, first trace the path from the positive terminal of the power source through each component and back to the negative terminal. Check whether the loop is complete — if there is any break, no current flows. Then identify whether components are in series (one path) or parallel (branching paths).

What do students usually get wrong about Circuit?

A switch works by physically breaking the circuit (open = off, closed = on).

How Circuit Connects to Other Ideas

To understand circuit, you should first be comfortable with electric current and voltage. Once you have a solid grasp of circuit, you can move on to series circuit, parallel circuit, circuit diagram and kirchhoffs laws.

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