what is Open circuit and short circuit? types, definition

Open circuit and short circuit

What is an Open Circuit? |

An open circuit means there is a break or gap in the path where electricity should flow. Imagine a road where a bridge is broken — cars can’t pass through it. In the same way, when a wire or part of the circuit is broken, electric current can’t flow.

✅ Simple Definition:

An open circuit is a circuit that is not complete. This means electricity has no way to move from one end to the other.

🧠 How Does It Work?

When a circuit is open:

• No current flows.
• The path is broken or interrupted.
• It has very high resistance — we say infinite resistance (∞).
• Ohm’s Law tells us:
  R = V / I
  But if current (I) is zero, the resistance becomes infinity.

🔧 Why Does a Circuit Become Open?

An open circuit can happen for many reasons:

• A wire might break.
• A switch might be turned off.
• A part might fail or burn out.
• The connection might come loose.

All of these cause the electricity to stop moving, just like a car stuck at a broken bridge.

🛠 Real-Life Example:

Think of a flashlight. If the battery is missing or the switch is off, the light won’t turn on. That’s an open circuit — the path is broken, so no electricity flows.

💡 Key Points to Remember

• Open circuit = No flow of current
• Caused by breaks or faults in the path
• Has infinite resistance
• Can happen in any electrical device if the connection is broken

types of Open circuit

1. Open Circuit in a Series Circuit.

Imagine you have a simple series circuit – like a line of friends holding hands. Current flows smoothly from one friend to the next. But what if one friend lets go? The chain breaks, and nothing moves forward. That’s exactly what happens in an open circuit.

Understanding the Concept

In a series circuit, all components are connected one after the other. So, if any one component gets damaged or disconnected, the whole circuit stops working. This is called an open circuit.

Let’s take an example.

Suppose we have five resistors: R1, R2, R3, R4, and R5 connected in a series with a battery of 120V. Now, if R4 burns out or the wire around it breaks, the path for current is broken. This is called an open circuit fault.

What Happens When There is an Open in a Series Circuit?

Here are some clear and simple effects:

1. Circuit Current Becomes Zero

As soon as the circuit opens, the current can no longer flow. Just like water stops flowing when a pipe breaks. So, the circuit current becomes zero.

2. No Voltage Drop Across Working Resistors

Even if the other resistors (R1, R2, R3, and R5) are perfectly fine, there will be no voltage drop across them, because no current is flowing.

3. Full Voltage Appears Across the Break

The total voltage from the battery appears across the open part. In our example, since the battery is 120V and the circuit is open at R4, we will get 120V across the break. That’s because nothing else is using the voltage.

4. Source Voltage May Look Higher

Since the current is zero, there’s no voltage drop in the internal resistance of the battery. So, when we measure the voltage at the battery terminals, it might appear higher than normal.

Why Does an Open Circuit Happen?

An open circuit can be caused by:

• A burnt resistor (like R4 in our example)
• A loose or broken wire
• A damaged component
• Poor soldering or broken path on a circuit board

This is known as component failure or breaking of a conducting path.

How to Detect an Open Circuit?

• Check if current is zero
• Look for voltage only across the faulty part
• Other components show no activity
• Visual inspection may show burnt or broken parts

2. Open Circuit in a Parallel Circuit

An open circuit in a parallel circuit happens when the connection in one or more branches breaks. This break can be caused by a component failure, like a burnt resistor, or disintegration of a conducting path, such as the breaking of a wire.

Imagine a simple parallel circuit with three branches. Each branch has one resistor — R1, R2, and R3. Now, let’s say resistor R3 gets damaged. It burns out and its resistance becomes infinite — that means no current can flow through it anymore. This is called an open circuit in that branch.

What Happens When a Branch is Open?

When a branch in a parallel circuit is open, the following things can be observed:

1. No current flows in the open branch
   Since R3 is open, the current I3 becomes zero. The electricity cannot pass through an open path.
2. Total current in the circuit becomes less
   The overall current drawn from the power supply will decrease because one path is no longer working.
3. Other branches work normally
   The branches with R1 and R2 are still complete, so they will continue to operate as usual. Nothing changes for them.
4. The broken device stops working
   Whatever was connected in the open branch — like a lamp or a motor — will not work. If it’s a lamp, it won’t glow. If it’s a motor, it won’t run.

Why Do Open Circuits Happen?

Open circuits usually happen due to:

• Burnt-out components (like a resistor or bulb)
• Broken wires or loose connections
• Aging or damaged materials in the circuit

This is known as component failure or disintegration of a conducting path. It’s like cutting a road that cars use to travel — traffic (or current) can’t pass through anymore.

Key Points to Remember

• A parallel circuit allows current to flow in multiple paths.
• If one path breaks, it does not stop the whole circuit, only that one branch.
• The total current reduces, but other devices keep working.
• Always check for broken wires or damaged parts if something stops working in a parallel setup.

Short Circuit –

A short circuit happens when electricity finds a quick and easy path to flow—one that it should not take. This path has very low resistance, which means a lot of current starts flowing suddenly. This is dangerous and can damage wires, components, or even start a fire.

💡 What Is a Short Circuit?

A short circuit is a mistake in the path of electric current. Normally, current flows through proper wires and components that have resistance. But in a short circuit, the electricity skips those parts and flows through a shortcut that offers almost no resistance.

Because of this, the current becomes very high—much higher than what the circuit is designed for. This sudden rush of current can heat up wires, burn components, or even cause sparks.

⚠️ What Causes a Short Circuit?

Short circuits happen when there is a fault in the circuit. Some common reasons are:

• 🔌 Insulation failure – When the plastic or rubber coating on wires wears out or melts, the wires may touch each other.
• ⚙️ Component failure – If a part like a resistor, capacitor, or switch breaks, it may create a shortcut for the current.
• 🔧 Loose or broken wires – If a wire breaks or its metal path gets exposed, it may connect wrongly and form a short path.
• 🔩 Metal pieces touching – Sometimes, two parts that should not touch come into contact and create a direct connection.

🔁 What Happens During a Short Circuit?

When a short circuit occurs:

1. The resistance in the circuit becomes very low.
2. The current suddenly increases.
3. The wires or parts may heat up quickly.
4. Components may burn, melt, or break.
5. If not stopped in time, it can cause serious damage or even a fire.

🛑 How to Prevent Short Circuits?

To stay safe from short circuits, we must:

• Use good quality insulated wires.
• Never overload a socket or plug.
• Keep all connections tight and clean.
• Replace old or damaged wires immediately.
• Use fuses or circuit breakers to stop extra current.
  
  TYPES OF SHORT CIRCUITS

1. Partial Short in a Series Circuit.

A partial short in a series circuit happens when an extra path is wrongly added between two points of the circuit. This new path skips one or more parts (like a resistor) that were supposed to be there. Because of this, the current doesn’t pass through the full circuit as it should. Let’s understand this with an easy example.

🔌 Simple Example:

Imagine a series circuit with three resistors: R1, R2, and R3, all connected in line. Now, due to a fault, a wire accidentally connects R1 directly to R3, skipping R2.

This kind of fault is called a partial short circuit.

What Happens in a Partial Short Circuit?

1. The circuit resistance goes down
   Since R2 is skipped, there is less resistance in the path. Less resistance means more current will flow in the circuit.
2. The current becomes too high
   Because the path is now easier (less resistance), more current flows than normal. This is dangerous.
3. Other components get overloaded
   The resistors that are still in the path (R1 and R3) get more current than they are designed for. This causes them to heat up too much.
4. Voltage drop increases on remaining components
   Since the current is high, the voltage drop across R1 and R3 also increases. This makes the components work harder than they should.
5. Risk of burning or failure
   The extra power (heat) may cause component failure. That means the resistor or any part of the circuit might get burnt or damaged. In simple words, it can stop working.

🔥 Why is a Partial Short So Dangerous?

Even though only a small change happened (a wire connecting the wrong parts), the whole circuit can get damaged. This may lead to:

• Overheating
• Component damage
• Wire melting
• Circuit failure
• Even fire, in serious cases

What Causes Partial Short Circuits?

• A wire touching the wrong part
• Component disintegration (parts breaking apart)
• Broken wire or loose connection
• Poor installation or wear and tear

2. Dead Short in a Series Circuit

Imagine you have a toy train track, and you’ve placed some small blocks (resistors) on the track that slow the train down a little. Now, suddenly, someone removes all those blocks and makes a new path that lets the train go straight without any stops. This is what we call a dead short.

In an electric circuit, when all the resistors (loads) are removed or bypassed by a wrong or unwanted path, the electricity gets a shortcut to run through. This shortcut has almost no resistance, which means nothing is stopping the flow.

As a result, the current (flow of electricity) becomes very high—too high! If there’s nothing like a fuse or circuit breaker to stop it, dangerous things can happen—like wires getting hot, smoke, fire, or even a blast. That’s why this is very risky and must be fixed right away.

🟡 3. Partial Short in a Parallel Circuit.

Now think of a playground with three slides (parallel branches). Kids (electric current) usually go down each slide equally. But one day, someone secretly opens a new shortcut that’s easier and faster than the slides.

Now what happens? Most of the kids rush through that shortcut, and fewer kids go down the proper slides. This shortcut is like a partial short in a parallel electric circuit.

In such a case, the total resistance of the circuit goes down, and the total current becomes more than normal. But the original slides (branches) still work—just not as well. They don’t get enough kids (current) as they should.

So even though the circuit still works a little, it’s not safe or correct. It can cause some parts to get damaged or stop working over time.

4. Dead Short in a Parallel Circuit.

Imagine you have three small bulbs connected in such a way that each one has its own path to electricity. This setup is called a parallel circuit. Now, think of what happens if suddenly, a wire connects the two ends of the power supply directly—without going through any bulb or load.

This is called a dead short.

✅ What Happens in a Dead Short?

In a dead short:

• All the bulbs stop working.
• The electricity takes the easiest path—the short path—and skips everything else.
• This new path has almost no resistance.
• Because there’s no resistance, the current becomes extremely high—so high that it can damage the entire circuit.

⚠️ Why Is It Dangerous?

When the current becomes too high:

• Wires can melt.
• Parts of the circuit can burn.
• There could be smoke, sparks, or even fire.
• Expensive devices can be completely ruined.

That’s why we use fuses or circuit breakers—they stop the flow of extra current and keep everything safe.

🧯 Causes of a Dead Short

A dead short can happen due to:

• A broken wire that touches another wire by mistake.
• A metal object falling on open wires.
• Component failure, like a damaged switch or burnt resistor.
• Disintegration of the conducting path, which means a wire breaks and connects in the wrong place.

Stay Safe from Dead Shorts

• Always use good-quality wires.
• Install fuses or circuit breakers in every circuit.
• Never leave wires uncovered or hanging.
• Call a trained electrician if something feels wrong.

🌟 Summary (Easy to Remember)

Duality Between Series and Parallel Circuits –

Have you ever looked at two things that seem different but follow the same pattern? Just like that, in electricity, series circuits and parallel circuits are different, but they follow a very special relationship. This relationship is called duality.

Let’s understand it in the easiest way possible.

💡 What is Duality?

Duality means two things that look different but behave in the same way mathematically. The rules that apply to one, also apply to the other, just with a little change.

In electricity, series circuits and parallel circuits are duals of each other. That means if you know how one works, you can easily understand the other by swapping a few terms.

⚡ Series Circuit: What Happens Here?

In a series circuit, all the electrical parts are connected one after the other, like train coaches.

Here’s what happens:

• Current (I) is the same in all parts.
  👉 I = I₁ = I₂ = I₃ = …
• Voltage (V) is shared across the parts.
  👉 V = V₁ + V₂ + V₃ + …
• Resistance (R) adds up.
  👉 Rₛ = R₁ + R₂ + R₃ + …

💡 So, in a series circuit:
➡ One path for current,
➡ Voltage gets divided,
➡ Resistance adds up.

🔌 Parallel Circuit: What Happens Here?

In a parallel circuit, the electrical parts are side by side, like branches of a tree.

Here’s what happens:

• Voltage (V) is the same everywhere.
  👉 V = V₁ = V₂ = V₃ = …
• Current (I) is shared between parts.
  👉 I = I₁ + I₂ + I₃ + …
• Conductance (G) adds up (Conductance is the opposite of resistance).
  👉 Gₚ = G₁ + G₂ + G₃ + …

💡 So, in a parallel circuit:
➡ Many paths for current,
➡ Voltage stays the same,
➡ Conductance adds up.

🔁 How Are They Duals?

Now comes the interesting part:

If you swap these three things, the series and parallel circuits turn into each other:

| In Series Circuit → Change to → In Parallel Circuit |
|——————|—————-|——————|
| Current (I) → becomes → Voltage (V) |
| Voltage (V) → becomes → Current (I) |
| Resistance (R) → becomes → Conductance (G) |

So basically:

• Voltage ↔ Current
• Resistance ↔ Conductance
• Series ↔ Parallel

This matching relationship is called duality.

🎯 Why is Duality Important?

Understanding duality helps us solve circuits easily. If you know the answer for a series circuit, you can quickly figure out the answer for a parallel one—just flip the rules!

🔄 Other Dual Examples

• Short circuit and open circuit are duals.
• Nodes and meshes in circuit diagrams are duals too.

Sometimes, a circuit stops working because of a component failure—like when a wire breaks or a path disintegrates. This is called open circuit (if the path is broken) or short circuit (if the path allows too much current). Knowing series and parallel duality helps in fixing such problems too.

✅ Final Words

So, remember:

Series and parallel circuits are different in design, but twins in behavior.
This twin-like relationship is called duality.

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