Electricity and magnetism form a single, unified branch of physics — electromagnetism — and they surface in judiciary general-knowledge papers in two distinct ways. First, as pure science: the meaning of charge, current, voltage, resistance, the laws of Ohm, Coulomb and Faraday, and the SI units that quantify them. Second, as the factual substratum of an entire statutory regime — the Electricity Act, 2003, the offence of theft of electricity, and a rich vein of Supreme Court authority on how that offence is tried. This chapter binds the two together, giving you exam-ready physics alongside the leading Indian case law so that a single read prepares you for both the science MCQs and the law-adjacent questions that examiners increasingly favour. Read it alongside General Physics and return to the Science and Technology hub for the full syllabus map.

Electric Charge and Coulomb's Law

Electric charge is the fundamental physical property of matter that causes it to experience a force in an electromagnetic field. Charge comes in two kinds — positive (carried by the proton) and negative (carried by the electron) — and like charges repel while unlike charges attract. Charge is quantised: it exists only as integer multiples of the elementary charge e, whose value is fixed by definition at exactly 1.602176634 × 10−19 coulombs since the 2019 revision of the SI. Charge is also conserved: in any isolated system the total charge neither increases nor decreases.

The force between two stationary point charges is governed by Coulomb's law, formulated by the French physicist Charles-Augustin de Coulomb in 1785. It states that the electrostatic force is directly proportional to the product of the magnitudes of the charges and inversely proportional to the square of the distance between them, acting along the line joining them. The proportionality constant in a vacuum is roughly 8.99 × 109 N·m2/C2. The inverse-square form mirrors Newton's law of gravitation, a parallel examiners enjoy testing. The SI unit of charge is the coulomb (C); one coulomb is the quantity of charge transported by a current of one ampere in one second.

Current, Voltage and Resistance

Electric current is the rate of flow of electric charge through a conductor; conventional current is taken to flow from the positive to the negative terminal, even though the actual carriers in a metal are negatively charged electrons drifting the opposite way. The SI unit of current is the ampere (A), one of the seven base units. Voltage, or potential difference, is the work done per unit charge in moving charge between two points; its unit is the volt (V), equal to one joule per coulomb. Resistance measures a conductor's opposition to current flow and is measured in ohms (Ω).

These three quantities are linked by Ohm's law, stated by Georg Simon Ohm in 1827: the current through a conductor between two points is directly proportional to the voltage across the two points, provided physical conditions such as temperature remain constant. Written as V = I × R, it is the single most tested relationship in this chapter. Materials that obey it are called ohmic conductors; semiconductors and diodes are non-ohmic. Electrical power dissipated is P = V × I = I2R, measured in watts, and the commercial unit of electrical energy is the kilowatt-hour — the very unit on which billing, and therefore the theft litigation discussed below, ultimately turns.

Conductors, Insulators and Semiconductors

Materials are classified by how readily they permit charge to flow. Conductors such as copper, silver and aluminium have loosely bound free electrons and offer little resistance, which is why copper is the workhorse of transmission lines. Insulators such as rubber, glass, dry wood and most plastics have tightly bound electrons and resist current strongly, making them indispensable for cable sheathing and safety equipment. Between these extremes lie semiconductors such as silicon and germanium, whose conductivity can be precisely controlled by adding impurities — a process called doping — and which underpin every transistor, diode and integrated circuit.

For judiciary papers the semiconductor's behaviour matters because it explains the entire electronics revolution and connects this chapter to General Chemistry, where atomic structure and bonding are treated. Superconductors — materials that lose all electrical resistance below a critical temperature — represent a fourth category and are a favourite source of trick questions; remember that zero resistance, not merely low resistance, is their defining feature.

Electric Circuits — Series and Parallel

A circuit is a closed loop through which current flows from a source such as a cell or battery. In a series circuit the components are connected end to end so that the same current passes through each; the total resistance is the simple sum of the individual resistances, and if one element fails the whole circuit breaks — the reason old fairy-light strings went entirely dark when a single bulb blew. In a parallel circuit the components share the same two nodes, so each has the full source voltage across it; the reciprocal of the total resistance equals the sum of the reciprocals, the total resistance is always less than the smallest branch resistance, and one branch failing leaves the others working. Household wiring is therefore parallel.

Two conservation principles, Kirchhoff's laws, govern any circuit: the junction (current) law states that the total current entering a node equals the total leaving it, expressing conservation of charge; the loop (voltage) law states that the sum of potential differences around any closed loop is zero, expressing conservation of energy. Safety devices — the fuse, which melts when current exceeds a rated value, and the miniature circuit breaker (MCB), which trips electromagnetically — are connected so as to interrupt the live wire, a practical detail that ties directly to the statutory safety standards prescribed by the Central Electricity Authority.

Magnetism and Magnetic Fields

Magnetism is the force exerted by magnets when they attract or repel one another. Every magnet has two poles — north and south — and, crucially, magnetic poles always occur in pairs: cutting a bar magnet in half yields two smaller magnets, never an isolated pole. This is why no magnetic monopole has ever been observed, a fact that distinguishes magnetism from electricity, where isolated charges are commonplace. Like poles repel and unlike poles attract, paralleling the rule for electric charges.

The region around a magnet in which its influence is felt is the magnetic field, conventionally depicted by field lines that run from north to south outside the magnet and form continuous closed loops. The SI unit of magnetic flux density (the B-field) is the tesla (T), named after Nikola Tesla; the older CGS unit is the gauss, with one tesla equal to ten thousand gauss. Magnetic flux itself is measured in webers (Wb), one weber being one tesla per square metre. The Earth behaves as a giant bar magnet whose magnetic poles lie near, but not exactly at, the geographic poles — which is why a compass needle aligns roughly north-south, a phenomenon explored further in geography papers.

The decisive insight of nineteenth-century physics was that electricity and magnetism are two faces of one phenomenon. In 1820 the Danish physicist Hans Christian Oersted noticed, during a lecture demonstration, that a current-carrying wire deflected a nearby compass needle — proof that an electric current produces a magnetic field. The direction of that field is given by the right-hand thumb rule: point the thumb along the conventional current and the curled fingers show the field's circulation. Coiling the wire into a solenoid concentrates the field and creates an electromagnet whose strength can be switched on and off and varied by changing the current — the basis of relays, electric bells, cranes and loudspeakers.

The converse effect — that a magnetic field exerts a force on a current-carrying conductor — is captured by Fleming's left-hand rule and is the operating principle of the electric motor, which converts electrical energy into mechanical energy. The complete mathematical unification was achieved by James Clerk Maxwell, whose equations of the 1860s showed that light itself is an electromagnetic wave. This unity of the field is the conceptual heart of the chapter and a frequent source of conceptual MCQs distinguishing the motor effect from induction.

Electromagnetic Induction and Faraday's Law

If a current produces a magnetic field, can a magnetic field produce a current? Michael Faraday answered yes in 1831 with the discovery of electromagnetic induction. Faraday's law states that a changing magnetic flux through a circuit induces an electromotive force (EMF) in that circuit, the magnitude of the induced EMF being proportional to the rate of change of flux. Lenz's law supplies the direction: the induced current always flows so as to oppose the change that produced it — a direct expression of the conservation of energy.

Electromagnetic induction is arguably the most economically consequential discovery in this chapter, because it is the principle behind the electric generator, which converts mechanical energy into electrical energy, and the transformer, which steps voltage up for long-distance transmission and down for safe domestic use. Every power station — thermal, hydro, nuclear or wind — ultimately relies on Faraday's induction to generate the electricity whose distribution is regulated by the Electricity Act, 2003. The journey from a deflected compass needle to a national grid is therefore a single chain of physics, and examiners reward candidates who can trace it.

SI Units and the Scientists Behind Them

Judiciary papers reliably test the SI units of electromagnetism and the scientists they honour. The ampere (current) recalls Andre-Marie Ampere; the volt (potential difference) Alessandro Volta, inventor of the first chemical battery; the ohm (resistance) Georg Simon Ohm; the coulomb (charge) Charles-Augustin de Coulomb; the watt (power) James Watt; the farad (capacitance) Michael Faraday; the henry (inductance) Joseph Henry; the tesla (magnetic flux density) Nikola Tesla; and the weber (magnetic flux) Wilhelm Eduard Weber. The hertz (frequency), though general, governs the 50-hertz alternating current standard adopted across India.

A landmark of modern metrology, frequently flagged as current affairs, is the 2019 revision of the SI, effective 20 May 2019, which redefined the ampere by fixing the numerical value of the elementary charge rather than by reference to the force between two parallel wires. This shift from a physical artefact-and-experiment basis to fundamental constants is the same conceptual move that redefined the kilogram, and it connects this chapter to the measurement themes in General Physics.

The Electricity Act, 2003 — Statutory Framework

The science of electricity becomes law through the Electricity Act, 2003, which received Presidential assent on 26 May 2003 and commenced on 10 June 2003. It consolidated and replaced the older trio — the Indian Electricity Act, 1910, the Electricity (Supply) Act, 1948, and the Electricity Regulatory Commissions Act, 1998 — into a single code governing the generation, transmission, distribution, trading and use of electricity. Its declared objects include promoting competition, protecting consumer interests, rationalising tariffs and ensuring transparent subsidy policy.

The Act establishes an institutional architecture that recurs in GK papers: the Central Electricity Authority (CEA), constituted under Section 70, which advises government and prescribes technical and safety standards; the Central and State Electricity Regulatory Commissions, which fix tariffs and license operators; and the Appellate Tribunal for Electricity (APTEL), which hears appeals from the Commissions. Safety standards for plants, lines, metering and grid connectivity are prescribed by the CEA, giving statutory teeth to the very circuit-safety physics discussed earlier in this chapter.

Theft of Electricity — Section 135

Because electricity is intangible, its dishonest abstraction posed a conceptual puzzle for the criminal law, resolved by treating it as a distinct statutory offence rather than ordinary theft of movable property. Section 135 of the Electricity Act, 2003 makes it an offence to dishonestly tap, tamper with a meter, bypass the meter, or otherwise make unauthorised use of electricity with intent to avoid payment. The defining ingredient is dishonest intention. The Act prescribes graded penalties: for theft of load not exceeding ten kilowatts the fine on a first conviction shall not be less than three times the financial gain, rising to not less than six times on a second or subsequent conviction.

Section 135 must be distinguished from Section 126, which deals with the civil consequence of unauthorised use of electricity — here an assessing officer provisionally assesses the charges payable to the best of his judgement, without any requirement of dishonest intent. The crucial line, as the Supreme Court has confirmed, is that theft under Section 135 necessarily carries the ingredient of dishonesty, whereas Section 126 assessment is a revenue-recovery mechanism. Special courts may be constituted under Section 153 to try electricity offences expeditiously, reflecting the legislature's concern with rampant pilferage.

Leading Case Law on Electricity Offences

The foundational authority on prosecuting electricity theft is Avtar Singh v. State of Punjab, decided by the Supreme Court on 24 August 1964 under the predecessor Indian Electricity Act, 1910. The appellant's conviction for theft of energy was set aside because the prosecution had not been instituted at the instance of the authority specified by Section 50 of that Act; the Court held that even though dishonest abstraction of energy was an offence, the special procedural requirement was mandatory and a prosecution launched without it was incompetent. The case remains the classic illustration of the principle that special statutes may impose procedural pre-conditions whose breach is fatal to the prosecution.

The leading modern authority is U.P. Power Corporation Ltd. v. Anis Ahmad, reported at AIR 2013 SC 2766, decided on 1 July 2013. A three-Judge consideration of consumer jurisdiction, the Court held that a person indulging in unauthorised use of electricity is not a 'consumer' raising a 'complaint' within the Consumer Protection Act, 1986, so that a challenge to an assessment order under Section 126, or to action under Sections 135 to 140, is not maintainable before a Consumer Forum. The proper remedy lies in the appellate machinery of the Electricity Act itself. The decision is regularly tested for its sharp separation between consumer-protection jurisdiction and the self-contained Electricity Act regime.

Everyday Applications and Electrical Safety

The principles in this chapter saturate daily life. Transformers at every substation rely on Faraday induction; motors in fans, pumps and trains exploit the motor effect; generators in every power plant invert it; electromagnets lift scrap and ring doorbells; and capacitors store charge in countless devices. The transmission of power at high voltage to minimise line losses (since loss equals I2R, reducing current by raising voltage cuts waste) is a direct application of Ohm's and Joule's laws to national infrastructure.

Electrical safety, too, is physics made statutory. Earthing diverts fault currents harmlessly to the ground; fuses and MCBs interrupt dangerous overcurrents; and the residual-current device (RCD or ELCB) detects leakage and disconnects within milliseconds, preventing fatal shocks. The CEA's safety regulations under the Electricity Act, 2003 mandate such protections, and electrocution-related liability frequently engages the law of negligence and the strict-liability principles studied alongside the public-health themes in Human Biology and Health. Understanding why a current path through the human body is dangerous — and how protective devices break it — closes the loop between the science and its legal regulation.

Exam Focus and Quick Revision

For rapid revision, lock in these high-yield facts. Ohm's law: V = I × R. Power: P = VI = I2R. Charge is quantised and conserved; the elementary charge is 1.602176634 × 10−19 C. Coulomb's law is inverse-square, like gravity. Series circuits add resistances; parallel circuits add reciprocals and lower total resistance. Oersted (1820) showed current produces a magnetic field; Faraday (1831) showed a changing field produces current; Lenz's law gives the opposing direction; Maxwell unified the theory and showed light is electromagnetic.

On the law side: the Electricity Act, 2003 commenced on 10 June 2003 and created the CEA, the Regulatory Commissions and APTEL; Section 135 punishes theft of electricity (dishonest intention essential), Section 126 covers unauthorised use (assessment, no dishonesty needed); Avtar Singh v. State of Punjab (1964) shows that mandatory procedural sanctions cannot be ignored; and U.P. Power Corporation Ltd. v. Anis Ahmad (AIR 2013 SC 2766) bars Consumer Forum jurisdiction over Section 126 and 135 matters. Pair this chapter with General Physics and the Science and Technology hub to consolidate the wider syllabus.

Frequently asked questions

What is the difference between Section 126 and Section 135 of the Electricity Act, 2003?

Section 135 creates the criminal offence of theft of electricity, whose essential ingredient is dishonest intention to avoid payment, attracting fine and imprisonment. Section 126 is a civil mechanism dealing with unauthorised use of electricity, where an assessing officer provisionally assesses charges payable without any need to prove dishonesty. The Supreme Court drew this line clearly in U.P. Power Corporation Ltd. v. Anis Ahmad, AIR 2013 SC 2766.

Can a consumer challenge an electricity assessment order before a Consumer Forum?

No. In U.P. Power Corporation Ltd. v. Anis Ahmad (AIR 2013 SC 2766), the Supreme Court held that a person indulging in unauthorised use of electricity is not a 'consumer' raising a 'complaint' under the Consumer Protection Act, 1986. Challenges to assessment under Section 126, or to action under Sections 135 to 140, are not maintainable before a Consumer Forum; the remedy lies within the Electricity Act's own appellate machinery.

What does Ohm's law state and what is its formula?

Ohm's law, stated by Georg Simon Ohm in 1827, says that the current through a conductor between two points is directly proportional to the voltage across them, provided physical conditions such as temperature stay constant. The formula is V = I × R, where V is voltage in volts, I is current in amperes and R is resistance in ohms. Materials that obey it are 'ohmic'; diodes and semiconductors are non-ohmic.

Who discovered the link between electricity and magnetism?

Hans Christian Oersted demonstrated in 1820 that an electric current deflects a compass needle, proving that a current produces a magnetic field. Michael Faraday discovered the converse in 1831 — that a changing magnetic field induces a current (electromagnetic induction). James Clerk Maxwell unified the two in his equations of the 1860s, showing that light itself is an electromagnetic wave.

How was the ampere redefined in 2019?

Under the 2019 revision of the SI, effective 20 May 2019, the ampere is defined by fixing the numerical value of the elementary charge e at exactly 1.602176634 × 10−19 coulombs. This replaced the older definition based on the force of 2 × 10−7 newtons per metre between two parallel current-carrying wires, shifting the basis from an experimental force measurement to a fixed fundamental constant.

Why is household wiring connected in parallel rather than in series?

Parallel wiring ensures every appliance receives the full supply voltage and operates independently — if one device fails or is switched off, the others keep working, unlike a series circuit where a single break stops the whole loop. Parallel connection also allows each branch to draw the current it needs. This is why home circuits, protected by fuses or MCBs on the live wire, are wired in parallel.