🧲 Physics II: Electricity & Magnetism

What you’ll learn

1. Static ElectricityIntroduce electric charge and static phenomena.Charge comes in positive and negative kinds, with like charges repelling and opposites attracting, and rubbing transfers electrons to create static. Lightning is the same charge-separation physics on an enormous scale.
2. Coulomb’s LawState the inverse-square force law between charges.Coulomb’s law gives the force between charges as proportional to their product and inversely to the square of their distance, measured with a torsion balance in the 1780s. An electroscope makes charge visible through repelling metal leaves.
3. The Electric FieldDescribe electric fields, field lines, and shielding.A charge fills surrounding space with an electric field that other charges feel, pictured with field lines from positive to negative. Conductors rearrange charge to cancel internal fields, the Faraday-cage effect.
4. Voltage and PotentialDefine voltage and connect it to Volta’s battery.Voltage is the energy per unit charge between two points, the pressure that drives current. Volta’s 1800 voltaic pile gave the first steady current, and large voltages pose real danger.
5. CapacitanceExplain how capacitors store charge and energy.A capacitor stores charge on two conductors separated by an insulator, holding energy in the field between them, from the early Leyden jar to modern chips. Capacitors smooth voltages, time signals, and power camera flashes.
6. Electric CurrentDefine current and its measurement.Current is the flow of charge, usually electrons through a wire, measured in amperes, and Ampère tied current to magnetic force in the 1820s. An ammeter placed in the path reads the flow.
7. Resistance and Ohm’s LawRelate voltage, current, and resistance via Ohm’s law.Resistance opposes current and turns electrical energy to heat, measured in ohms, and Ohm’s law V = IR makes current proportional to voltage. A current–voltage graph for fixed resistance is a straight line.
8. Series and Parallel CircuitsContrast series and parallel connections.Series components share one current on a single loop, so one failure stops all, while parallel components share voltage across independent branches. The two follow different rules for adding resistance, current, and voltage.
9. Power in CircuitsCompute electrical power and understand protection.Electrical power equals voltage times current in watts, appearing as heat and light in resistive elements. Fuses and breakers are deliberate weak points that cut dangerous currents.
10. MagnetismIntroduce magnetic poles and fields.Every magnet has north and south poles that attract and repel like charges, and poles cannot be isolated. Magnets act through a field, as a compass aligning with Earth’s field shows.
11. ElectromagnetismShow that currents create magnetic fields.Ørsted’s 1820 discovery that a current deflects a compass linked electricity and magnetism. Coiling wire into a solenoid with an iron core concentrates the field into a switchable electromagnet.
12. Magnetic Force and MotorsExplain the force on currents and how motors work.A magnetic field pushes sideways on a current-carrying wire, the force behind every motor, with a commutator reversing current to keep a loop spinning. Loudspeakers use the same force to move a cone and make sound.
13. Electromagnetic InductionState Faraday’s law of induction.Faraday found in 1831 that a changing magnetic field through a coil induces a current, the reverse of a motor. Only change induces current, and faster change, stronger magnets, or more turns increase it.
14. Generators and TransformersApply induction to generators and transformers.Generators spin coils in magnetic fields to produce nearly all electricity, while transformers use changing current in one coil to induce another and change voltage. Both work only through Faraday’s changing-field principle.
15. Electromagnetic WavesPresent Maxwell’s unification of light and electromagnetism.Maxwell showed oscillating electric and magnetic fields travel as waves at the speed of light, concluding light is electromagnetic. Radio, light, and X-rays are one spectrum differing only in wavelength.

Questions this course answers

Grounded in trusted sources

• OpenStax, 'University Physics, Volume 2' (openstax.org)
• Michael Faraday, 'Experimental Researches in Electricity' (1839–1855)
• James Clerk Maxwell, 'A Treatise on Electricity and Magnetism' (1873)
• Halliday, Resnick & Walker, 'Fundamentals of Physics'

Every Wunder lesson is built from real, reputable sources — never invented.

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