ESAT Physics: Revision Notes

P1.1

Electrostatics explains how stationary electric charges are created, typically on insulators, by the transfer of electrons. It covers the fundamental forces between these charges and the practical applications and hazards, such as static shocks and the importance of earthing for safety.

P1.2

Current, voltage and resistance are the three quantities that describe every electric circuit, and the relationships between them decide how energy and power flow. A frequently tested foundation for all circuit analysis.

P2.1

Magnets exert forces through a surrounding magnetic field, attracting or repelling other magnets and inducing magnetism in certain materials. These properties underpin compasses, motors and electromagnets.

P2.2

An electric current flowing through a conductor generates a magnetic field in the surrounding space. Understanding the shape, direction, and strength of these fields for different conductor arrangements, like straight wires and coils (solenoids), is fundamental to how electromagnets and motors work.

P2.3

A current-carrying wire placed in a magnetic field experiences a force — the motor effect. It is how a DC motor turns electrical energy into rotation, and the force direction follows Fleming's left-hand rule.

P2.4

Moving a wire through a magnetic field, or changing the field around it, generates a voltage — electromagnetic induction. This is the working principle behind electrical generators and transformers.

P2.5

Transformers are devices that use electromagnetic induction to change the voltage of an alternating current (AC) supply. They are crucial for adapting mains voltage for electronic devices and for transmitting electrical power efficiently over long distances.

P3.1

Kinematics is the study of how objects move, describing their path, speed, and acceleration without considering the forces involved. It is a foundational topic for solving almost all mechanics problems in the ESAT.

P3.2

Forces are pushes and pulls with both size and direction; combining them on a force diagram gives the resultant force, which decides whether an object stays still, speeds up or changes direction.

P3.3

Under a stretching force, materials deform either elastically (springing back) or permanently. Force-extension graphs, Hooke's law and the energy stored in a stretched spring quantify this behaviour.

P3.4

Newton's Laws describe the fundamental link between force and motion. They are the essential toolkit for solving nearly all classical mechanics problems by explaining why objects start moving, stop moving, or change direction.

P3.5

Mass measures how much matter an object contains, while weight is the gravitational force acting on it. As a falling object speeds up, air resistance grows until it balances weight and the object reaches terminal velocity.

P3.6

Momentum quantifies an object's motion and is defined by its mass and velocity. In any isolated interaction, like a collision or explosion, the total momentum of the system is always conserved, a key principle for solving problems in one dimension.

P3.7

Energy stored as kinetic and potential energy is transferred by doing work, and power measures how fast that transfer happens. These ideas connect force, motion and height in almost every mechanics problem.

P4.1

Conduction transfers heat through direct particle-to-particle contact, which is why metals conduct well and trapped air insulates. The rate of heat flow depends on a material's dimensions and the temperature difference across it.

P4.2

Convection is the transfer of thermal energy within fluids (liquids and gases) caused by the bulk movement of the fluid itself, driven by temperature-induced density changes.

P4.3

Every object emits and absorbs heat as infrared electromagnetic waves — thermal radiation, the only transfer that needs no medium. An object's colour, texture and temperature set how strongly it radiates and absorbs.

P4.4

Adding thermal energy raises an object's temperature by an amount that depends on its mass and material. Specific heat capacity is the energy needed to warm one kilogram of a substance by one degree.

P5.1

Treating solids, liquids and gases as particles in motion explains their everyday properties. The spacing, arrangement and movement of particles link the microscopic picture to what we observe.

P5.2

Gas pressure is the combined effect of countless particles colliding with their container. At constant temperature, squeezing a gas into a smaller volume raises its pressure — the inverse relationship known as Boyle's law.

P5.3

Changing state, such as melting or boiling, absorbs or releases energy without any change in temperature. This hidden energy, the latent heat, goes into rearranging particles rather than speeding them up.

P5.4

Density is a fundamental property of matter that quantifies how much mass is packed into a given volume. ESAT questions frequently test your ability to calculate density, handle unit conversions, and apply the concept to experimental scenarios without a calculator.

P5.5

Pressure is force spread over an area. The same idea gives the pressure under a solid object and the pressure deep in a fluid, which increases with depth, density and gravity.

P6.1

Waves carry energy from place to place without carrying matter with them. Wavelength, frequency, amplitude and the wave equation describe every wave, from sound to light.

P6.2

When waves meet a boundary they reflect and refract, changing direction as their speed changes; relative motion between a source and observer shifts the frequency in the Doppler effect.

P6.3

Ray diagrams predict the path of light as it reflects off mirrors and refracts through materials such as glass or water — the geometric foundation of optics.

P6.4

Sound waves are longitudinal vibrations that transfer energy through a medium, allowing us to hear. Their production, perception and reflection underpin technologies such as sonar and medical ultrasound.

P6.5

The electromagnetic (EM) spectrum is the continuous range of all possible frequencies of electromagnetic radiation. These notes cover the properties, order, applications, and hazards of its different parts, which is fundamental for questions on communications, energy transfer, and medical physics.

P7.1

Every atom is built from protons, neutrons and electrons, and nuclide notation records how many of each. Isotopes of an element differ only in neutron number — the starting point for all nuclear physics.

P7.2

Radioactivity describes the spontaneous breakdown of unstable atomic nuclei, which release energy and particles to become more stable. For the ESAT, this involves understanding the different types of decay and being able to balance nuclear equations to track changes in elements.

P7.3

Alpha, beta and gamma radiation differ in penetrating power, ionising strength and how electric and magnetic fields deflect them. These differences explain both their uses and their safety hazards.

P7.4

Radioactive decay describes how unstable atomic nuclei lose energy — a random process that, across a large population, is precisely modelled by half-life. Reading decay graphs and working through multi-step rate calculations is a core ESAT physics skill.