A device which is used in our TV set, Computer, Radio set for storing the electric charge is

1. Fundamentals of Electric Charge and Current (basic)

To understand electricity, we must start at the subatomic level. Everything around us is made of atoms, which contain electric charge. Charge is an intrinsic property of matter; protons carry a positive charge, while electrons carry a negative charge. In the SI system, charge (represented by Q) is measured in Coulombs (C). Interestingly, these charges aren't just static; when they move, they create what we call an electric current. It is this movement of charge that allows magnetic fields to exert forces on conductors Physical Geography by PMF IAS, Earths Magnetic Field, p.65.

Electric Current (I) is defined as the rate at which electric charge flows through a cross-section of a conductor. Think of it like water flowing through a pipe; the more water passing a point per second, the higher the current. Mathematically, I = Q/t, where t is time. The SI unit for current is the Ampere (A), named after André-Marie Ampère. One Ampere is equivalent to one Coulomb of charge flowing past a point every second.

However, charges do not move on their own; they require a "push" or an incentive to travel from one point to another. This push is provided by the Electric Potential Difference (V). We define potential difference between two points in a circuit as the work done (W) to move a unit charge from one point to the other Science, Class X (NCERT 2025 ed.), Electricity, p.173. The formula is:

V = W/Q

The SI unit of potential difference is the Volt (V). One volt is defined as the potential difference between two points when 1 Joule of work is done to move a charge of 1 Coulomb from one point to the other Science, Class X (NCERT 2025 ed.), Electricity, p.173.

Sources: Science, Class X (NCERT 2025 ed.), Electricity, p.173; Physical Geography by PMF IAS, Earths Magnetic Field (Geomagnetic Field), p.65

2. Electrical Conductors and Insulators (basic)

To understand electricity, we must first look at the tiny building blocks of all matter: atoms. At the center of an atom is the nucleus, surrounded by electrons. In some materials, the outermost electrons are held very loosely by the nucleus. These are called free electrons. When we apply an electrical force (like a battery), these free electrons can hop from one atom to another, creating a flow of charge. This fundamental behavior determines whether a material is a conductor or an insulator.

Conductors are materials that allow electric current to flow through them with ease. Most metals are excellent conductors because they possess a high density of these free electrons Science, Class VII, NCERT (Revised ed 2025), Electricity: Circuits and their Components, p.36. For instance, silver is the best conductor, followed closely by copper and aluminum. Because metals are also ductile (can be drawn into wires), they are the primary choice for creating electrical circuits Science, Class VII, NCERT (Revised ed 2025), The World of Metals and Non-metals, p.48. On the other hand, Insulators (or poor conductors) are materials where electrons are tightly bound to their atoms and cannot move freely. Materials like rubber, glass, and plastic prevent the flow of electricity, acting as a barrier.

In our daily lives, we use these materials in tandem for safety and efficiency. Consider an electric screwdriver: the internal metal part is a conductor to perform work, while the handle is covered in plastic or rubber Science, Class VII, NCERT (Revised ed 2025), The World of Metals and Non-metals, p.48. This insulation ensures that the electric current stays within the tool and does not pass through the user’s body, preventing electric shocks. Interestingly, while pure metals are great conductors, we sometimes use alloys (mixtures of metals) in devices like toasters because they offer more resistance, which helps generate the heat needed to brown your bread Science, Class X (NCERT 2025 ed.), Electricity, p.181.

Sources: Science, Class VII, NCERT (Revised ed 2025), Electricity: Circuits and their Components, p.36; Science, Class VII, NCERT (Revised ed 2025), The World of Metals and Non-metals, p.48; Science, Class X (NCERT 2025 ed.), Electricity, p.181

3. Basic Circuit Elements: Passive vs Active (basic)

In the world of electronics, we classify every component into two fundamental families: Active and Passive elements. Think of this distinction like a kitchen: the stove is an active element because it provides the heat (energy), while the pots, pans, and ingredients are passive because they only receive, store, or transform that energy.

Active elements are components capable of generating or amplifying electrical energy. They are the "movers" of the circuit. Common examples include batteries, generators, and transistors. A battery, for instance, provides the potential difference (voltage) necessary to push electrons through a conductor Science, Class X (NCERT 2025 ed.), Electricity, p.181. Without an active element, a circuit remains dormant because there is no source to sustain the flow of current.

Passive elements, on the other hand, cannot generate energy; they can only dissipate it, resist it, or store it in a field. The three pillars of passive components are:

• Resistors: These components hinder the flow of electrons, effectively "retarding" the current due to the attraction of atoms within the material Science, Class X (NCERT 2025 ed.), Electricity, p.177.
• Inductors: These store energy in a magnetic field when current passes through them.
• Capacitors: These are specialized devices designed to store electric charge and electrical energy. A capacitor consists of two parallel conducting plates separated by an insulator (dielectric). When a voltage is applied, charge builds up on the plates, a property known as capacitance.

Capacitors are particularly vital in modern electronics like your smartphone or TV. They act as tiny energy reservoirs that smooth out voltage fluctuations and protect sensitive internal parts from sudden electrical spikes. However, when these devices reach the end of their life, they become E-waste. Components like the solder on circuit boards often contain lead, which can be hazardous to the nervous and renal systems if not recycled scientifically Environment, Shankar IAS Academy (ed 10th), Environmental Pollution, p.92.

Sources: Science, Class X (NCERT 2025 ed.), Electricity, p.177, 181; Environment, Shankar IAS Academy (ed 10th), Environmental Pollution, p.92

4. Semiconductors and Modern Electronics (intermediate)

In our journey through electronics, we encounter components that act like the "plumbing" of a circuit. While resistors act as narrow pipes to limit flow, the capacitor acts like a pressurized water tank. It is a passive electronic component specifically designed to store electric charge and electrical energy in an electric field. Structurally, it consists of two parallel conducting plates separated by an insulating material known as a dielectric. The ability of this setup to hold a charge is called capacitance, measured in Farads (F).

Why is this storage so critical? In modern devices like smartphones, which utilize over 45 different elements including Silicon and Copper Science, Class VIII NCERT, Nature of Matter, p.124, the electrical supply isn't always perfectly steady. A capacitor acts as a buffer. In a television or computer, it "smooths" out voltage fluctuations—if the voltage from the wall outlet dips momentarily, the capacitor discharges its stored energy to fill the gap, ensuring the sensitive semiconductor chips don't crash. It also protects these components from sudden electrical spikes that could damage the delicate atomic structures of the materials Science, Class X NCERT, Metals and Non-metals, p.49.

Beyond smoothing, capacitors are essential for timing and filtering. For instance, the time it takes for a capacitor to charge or discharge can be used to control the blink of a turn signal or the flash of a camera. By storing charge electrostatically rather than chemically (like a battery), they can release their energy almost instantaneously, making them the primary energy storage choice for high-speed electronics.

Sources: Science, Class VIII NCERT, Nature of Matter, p.124; Science, Class X NCERT, Metals and Non-metals, p.49

5. Electromagnetic Induction and Inductors (intermediate)

In our previous steps, we explored how an electric current creates a magnetic field. Now, we look at the remarkable discovery that the reverse is also true: magnetism can create electricity. This phenomenon is known as Electromagnetic Induction. It occurs when a conductor, like a copper wire, is placed in a changing magnetic field, or when a conductor moves through a stationary magnetic field. This "magnetic effect of moving magnets" produces an induced current in the wire, a principle that forms the backbone of modern power generation Science, class X (NCERT 2025 ed.), Magnetic Effects of Electric Current, p.195.

An Inductor is a passive electronic component designed specifically to use this principle. It is typically a coil of conducting wire. While a straight wire produces a weak magnetic field, bending that wire into a circular loop concentrates the field lines at the center Science, class X (NCERT 2025 ed.), Magnetic Effects of Electric Current, p.200. When many such loops are combined (forming a solenoid), the device can store energy in the resulting magnetic field. To make these inductors even stronger for practical use, an iron core is often placed inside the coil, creating a powerful electromagnet Science, Class VIII, NCERT (Revised ed 2025), Electricity: Magnetic and Heating Effects, p.58.

The defining characteristic of an inductor is its "stubbornness"—it resists any change in the current flowing through it. If the current increases, the magnetic field expands, inducing a back-voltage that tries to slow the increase. If the current decreases, the collapsing magnetic field induces a voltage that tries to keep the current flowing. This property, called inductance, makes inductors vital for filtering signals and protecting circuits from sudden current surges. While a capacitor stores energy in an electric field, the inductor stores it in a magnetic field.

Sources: Science, class X (NCERT 2025 ed.), Magnetic Effects of Electric Current, p.195; Science, class X (NCERT 2025 ed.), Magnetic Effects of Electric Current, p.200; Science, Class VIII, NCERT (Revised ed 2025), Electricity: Magnetic and Heating Effects, p.58

6. Power Supply: AC to DC Conversion (intermediate)

In our daily lives, the electricity delivered to our homes via the service mains is Alternating Current (AC), typically at a voltage of 220 V Science, Class X (NCERT 2025 ed.), Electricity, p.194. However, the internal components of modern electronics like smartphones, computers, and LED TVs require Direct Current (DC)—a steady, one-way flow of electricity—to function without damage. The process of AC to DC conversion is what happens inside your charger or power adapter.

The transition from AC to DC isn't instantaneous; it involves a sequence of components. First, a rectifier (usually made of diodes) converts the bidirectional AC into a "pulsating" DC that only flows in one direction but still fluctuates wildly in strength. To turn these pulses into a smooth, steady line, we use a Capacitor. A capacitor is a passive component designed specifically to store electric charge and electrical energy. It acts like a temporary reservoir: it fills up with charge when the voltage is at its peak and releases that stored energy when the voltage dips, effectively "smoothing out" the fluctuations.

Understanding the distinction between various circuit components is vital for mastering electronics. While an electric fuse is designed to melt and break a circuit during a short-circuit to prevent damage from Joule heating Science, Class X (NCERT 2025 ed.), Magnetic Effects of Electric Current, p.205, the capacitor's role is different. It consists of two parallel conducting plates separated by an insulator (dielectric). Its capacity to hold charge, known as capacitance, allows it to filter signals and protect sensitive electronics from sudden electrical spikes.

Sources: Science, Class X (NCERT 2025 ed.), Electricity, p.194; Science-Class VII, NCERT (Revised ed 2025), Electricity: Circuits and their Components, p.27; Science, Class X (NCERT 2025 ed.), Magnetic Effects of Electric Current, p.205

7. Capacitance: Storing Electrical Energy (exam-level)

A capacitor is a passive electronic component designed to store electrical energy in an electric field. While a battery stores energy through chemical reactions and releases it slowly, a capacitor stores energy electrostaticly and can discharge it almost instantaneously. Structurally, the simplest capacitor consists of two parallel conducting plates separated by an insulating material known as a dielectric (such as air, ceramic, or plastic).

The ability of a component to hold an electric charge is known as capacitance (C). It is mathematically defined as the ratio of the magnitude of charge (Q) on either plate to the potential difference (V) applied across them. This relationship is expressed as:

C = Q / V

The SI unit for capacitance is the Farad (F). Because a Farad is a very large unit, most practical electronics use microfarads (μF) or picofarads (pF). To store charge, work must be done to move the electrons against the growing electric field between the plates; this work is then stored as electric potential energy Science, Class X (NCERT 2025 ed.), Electricity, p.173.

In everyday life, capacitors are essential "stabilizers." In television sets and computers, they act like small reservoirs that supply extra charge when the voltage drops and absorb it when the voltage spikes, protecting delicate circuits from damage. This is why they are found in almost all modern home appliances, from tube lights to complex digital displays Understanding Economic Development, Class X, NCERT (Revised ed 2025), Globalisation and the Indian Economy, p.67.

Sources: Science, Class X (NCERT 2025 ed.), Electricity, p.173; Science, Class X (NCERT 2025 ed.), Electricity, p.186; Understanding Economic Development, Class X, NCERT (Revised ed 2025), Globalisation and the Indian Economy, p.67

8. Comparing Resistors, Inductors, and Capacitors (exam-level)

In the study of electronics, we encounter three fundamental passive components that govern how electricity behaves: Resistors, Inductors, and Capacitors. Think of these as the essential 'plumbing' of a circuit. While a Resistor acts like a narrow pipe that limits flow, the Capacitor and Inductor act as storage tanks, though they hold energy in very different ways.

A Resistor is designed to oppose the flow of electric current. Its primary role is to dissipate electrical energy, usually turning it into heat. According to Ohm’s Law, the potential difference (V) across a resistor is directly proportional to the current (I) flowing through it (V = IR), provided the temperature remains constant Science, Class X, Electricity, p.192. The resistance (R) depends on the material's properties, its length, and its cross-sectional area Science, Class X, Electricity, p.192. We use resistors to control current levels and protect delicate components from excessive flow.

Unlike resistors, Capacitors and Inductors are energy storage devices. A Capacitor consists of two parallel conducting plates separated by an insulator. It stores energy in an electric field by holding an electric charge. This property, known as capacitance, allows it to act as a buffer—smoothing out voltage fluctuations in devices like computers and TVs to ensure a steady signal. Conversely, an Inductor (typically a coil of wire) stores energy in a magnetic field created by the current passing through it. While a capacitor resists sudden changes in voltage, an inductor resists sudden changes in current.

Sources: Science, Class X, Electricity, p.192

9. Solving the Original PYQ (exam-level)

Having just mastered the fundamentals of electromagnetism and circuit components, this question serves as a perfect application of those principles. While you have studied how electric fields behave, the capacitor is the specific hardware implementation designed to capture and hold that electrostatic energy. As discussed in NCERT Class 12 Physics (Electrostatic Potential and Capacitance), the ability of a system to store charge is its capacitance. In consumer electronics like TV sets and radios, these components act as essential reservoirs that stabilize voltage and filter noise by discharging energy exactly when the circuit requires it.

To arrive at the correct answer, (C) capacitor, your reasoning should focus on the specific physical mechanism of storage. A capacitor consists of two conducting plates separated by an insulator; charge builds up on these plates but cannot pass through, effectively 'storing' the electric potential. In contrast, UPSC includes resistor (Option A) as a trap because, while common, its role is to oppose the flow of current and dissipate energy as heat, rather than saving it. An inductor (Option B) is another common distractor; however, it stores energy in a magnetic field created by current flow, which is functionally different from storing static electric charge.

Finally, a conductor (Option D) is simply any material that allows electricity to move freely; it is the pathway, not the storage device. The key 'trigger phrase' in this question is storing electric charge. By distinguishing between dissipation (resistor), conduction (conductor), and magnetic storage (inductor), you can confidently isolate the capacitor as the only device intended for electrostatic storage in our daily gadgets.