Understanding Inductors and Inductance — How Magnetic Energy Is Stored

In electronic circuits, not all components respond instantly to changes. Some store energy and react over time. One such fundamental component is the inductor, which stores energy in a magnetic field and resists changes in current.

In this blog, we’ll understand what an inductor is, how it works, how it stores energy, and what inductance really means.

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⚙️ What is an Inductor?

An inductor is a passive electronic component that stores electrical energy in the form of a magnetic field.
It mainly opposes changes in current — just like a capacitor opposes changes in voltage.

Whenever current starts flowing through an inductor, it generates a magnetic field around it.
And when that current changes (increases or decreases), the magnetic field changes too — which in turn induces a voltage that tries to oppose that change.

That’s the fundamental nature of an inductor.

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🧱 Structure — How It’s Made

An inductor is typically made of:

1. A coil of wire — usually copper, wound in loops or turns.

2. A core — which can be air, iron, or ferrite placed inside the coil to enhance its magnetic properties.

3. Two terminals / leads — for connection to the circuit.

The more turns the coil has, and the better the core material, the stronger the magnetic field it can create — and hence, the higher the inductance.

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⚙️ How Does an Inductor Work?

Before any current flows:

• There is no magnetic field around the coil.

When a voltage source is connected:

1. Current starts flowing through the wire coil.

2. As current flows, a magnetic field forms around the coil (according to Ampere’s Law).

3. If the current keeps increasing, the magnetic field grows — but this change in magnetic flux induces an opposing voltage (back EMF) in the coil (as per Faraday’s Law of Electromagnetic Induction).

4. This induced voltage always acts in the opposite direction of the applied voltage — this is Lenz’s Law in action.

So what’s happening inside is that the inductor resists any change in current.

• If you try to increase current, it generates a voltage that opposes the increase.

• If you try to decrease current, it generates a voltage that tries to keep it flowing.

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💡 In Simple Words

• Capacitor → opposes change in voltage

• Inductor → opposes change in current

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🔋 Energy Storage in an Inductor

An inductor stores energy in the magnetic field created by the current flowing through it.

The moment you disconnect the source, this magnetic field collapses and releases energy back into the circuit.

The energy stored is given by:

E = ½ L I²

where:

• E = energy stored (joules)

• L = inductance (henries, H)

• I = current through the inductor (amperes)

Just like a capacitor stores energy in an electric field, an inductor stores it in a magnetic field.

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🧮 What is Inductance?

Inductance is the ability of an inductor to store magnetic flux per unit current.

In simple terms, it tells how much magnetic field (or magnetic flux) an inductor can produce for a given current flowing through it.

It is denoted by L and measured in Henries (H).

Mathematically:

L = NΦ / I

where:

• N = number of turns in the coil

• Φ = magnetic flux linked with the coil (Weber)

• I = current through the coil (amperes)

It basically tells us how much magnetic flux is produced for a given current.

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⚡ Voltage–Current Relationship

The voltage across an inductor is given by:

V = L (dI/dt)

This means:

• If the current changes rapidly, the induced voltage is large.

• If the current is steady, dI/dt = 0, so the voltage across the inductor is zero.

Once fully energized with DC, an inductor behaves like a short circuit.

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🧠 Factors Affecting Inductance

1. Number of Turns (N): More turns → higher inductance

2. Core Material: Iron or ferrite cores concentrate magnetic flux → higher inductance

3. Cross-sectional Area (A): Larger area → stronger field → higher inductance

4. Length of Coil (l): Longer coil → weaker field → lower inductance

For a solenoid:

L = (μ N² A) / l

where:

• μ = permeability of the core material

• N = number of turns

• A = cross-sectional area

• l = length of the coil

Here, μ (mu) plays a similar role as ε (epsilon) in capacitors — it tells how well the core supports the magnetic field.

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🧩 Summary Table

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🔚 Conclusion

An inductor is a fundamental passive component that stores energy in the form of a magnetic field and resists changes in current. By generating an opposing voltage whenever current changes, inductors play a critical role in controlling current flow in electronic circuits.

Inductance defines how effectively an inductor can store magnetic energy, and it depends on physical factors like the number of turns, core material, and coil geometry. Inductors are widely used in filters, power supplies, energy storage systems, and signal processing circuits.

Understanding inductors and inductance provides a strong foundation for learning AC circuits, RL circuits, transformers, and advanced analog electronics.

Understanding Capacitors and Capacitance — How Electrical Energy Is Stored

 In electronic circuits, energy is not only consumed — it can also be temporarily stored and released when needed. One of the most important components that makes this possible is the capacitor.

In this blog, we’ll understand what a capacitor is, how it works, how it stores energy, and what capacitance really means.

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⚙️ What is a Capacitor?

A capacitor is an electronic component that stores electrical energy in the form of an electric field.

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🧩 Structure — How It’s Made

A basic capacitor consists of three parts:

1. Two Conducting Plates – usually made of metal like aluminum or copper.

2. Dielectric Material – an insulating layer placed between the plates (air, paper, plastic, ceramic, or mica).

3. Leads / Terminals – used to connect the capacitor into a circuit.

So physically, a capacitor looks like two metal plates separated by a thin insulating film.

The dielectric does not conduct electricity — it helps store charge by preventing electrons from jumping directly from one plate to the other.

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⚡ How Does a Capacitor Work?

Before applying voltage:

• Both plates are electrically neutral, meaning they have an equal number of positive and negative charges.

After connecting the capacitor to a battery:

1. The negative terminal of the battery pushes electrons toward the bottom plate of the capacitor through the connecting wire.
   → This bottom plate starts accumulating extra electrons and becomes negatively charged.

2. As electrons pile up on the bottom plate, they repel electrons from the top plate (because like charges repel).

3. These repelled electrons from the top plate move through the external circuit toward the positive terminal of the battery, which is electron-deficient and attracts them.

4. The top plate, having lost electrons, becomes positively charged.

Meanwhile, the dielectric between the plates prevents direct electron flow — it only allows an electric field to form.

As charge separation builds up, a potential difference (voltage) develops across the plates.
This continues until the voltage across the capacitor equals the battery voltage — at that point, charging stops.

The electric field created between the plates stores the electrical energy.

The electric field strength is given by:

E = V / d

where:

• V = voltage across the plates

• d = distance between the plates

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🔋 Energy Storage in a Capacitor

The capacitor now holds energy in the electric field between its plates.

If the battery is disconnected, the charges remain stored — the capacitor stays charged.

It releases this stored energy only when a conductive path (like a resistor or load) is connected between its plates.
Electrons then flow from the negatively charged plate to the positively charged plate through the external circuit, producing current until both plates become neutral again.

This process is called discharging the capacitor.

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🧮 What is Capacitance?

Capacitance is the ability of a capacitor to store electric charge per unit voltage.

In simple terms, it tells how much charge a capacitor can store for a given applied voltage.

Mathematically:

C = Q / V

where:

• C = capacitance (Farads, F)

• Q = charge stored (Coulombs)

• V = voltage across the capacitor (Volts)

A higher capacitance means greater charge storage capability.

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⚡ Current–Voltage Relationship in a Capacitor

The relationship between current and voltage for a capacitor is:

I = C (dV/dt)

This means:

• If voltage changes rapidly, current is large.

• If voltage is constant, current is zero.

So a capacitor allows current to flow only when voltage is changing.
A capacitor opposes sudden changes in voltage.

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🧠 Factors Affecting Capacitance

1. Area of Plates (A): Larger area → more charge → higher capacitance

2. Distance Between Plates (d): Greater distance → lower capacitance

3. Dielectric Constant (ε): Better dielectric → higher capacitance

For a parallel plate capacitor:

C = ε (A / d)

From this:

• Bigger plates → higher capacitance

• Closer plates → higher capacitance

• Better dielectric → higher capacitance

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🔥 Energy Stored in a Capacitor

The energy stored in a capacitor is given by:

E = (1/2) C V²

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🔚 Conclusion

A capacitor is a fundamental electronic component that stores electrical energy in the form of an electric field. By separating charge across two plates using a dielectric, it plays a crucial role in energy storage, voltage stabilization, filtering, timing circuits, and signal coupling.

Capacitance defines how effectively a capacitor can store charge, and it depends on the physical structure and dielectric material used. Capacitors respond to changes in voltage rather than steady values, which makes them essential in both analog and digital electronics.

Understanding capacitors and capacitance lays a strong foundation for learning RC circuits, filters, power supplies, and advanced analog electronic systems.