Notes, summaries, assignments, exams, and exercises for Physics for Secondary education

The Oersted Experiment

The Oersted experiment involves placing a compass on a cord or wire. When no electric current flows through the wire, the compass needle points north, as it is guided by the Earth's magnetic field. However, when the cable is connected to an electrical generator (e.g., a battery), the compass needle deflects and becomes oriented perpendicular to the cable.

This phenomenon occurs regardless of the wire's orientation. Furthermore, if the direction of the current flowing through the cable is reversed, the compass needle will turn around, orienting itself perpendicular to the wire in the opposite direction.

The Discovery of Electromagnetism

This experiment demonstrates that an electric current creates a magnetic field around it....

Direction of Electric Current

If you consider the position of a compass needle around a conductor carrying an electric current, you can establish a relationship between the direction of the current and the resulting magnetic field.

Please note the following: Electricity flows due to the movement of electrons through the conductor. Even before the existence of electrons was discovered, the flow direction of the stream was established. It was agreed that the current runs from the positive terminal of a power source to the negative terminal. (The conventional sense of the current is opposite to the actual motion of electrons; we use the conventional sense of the current in analysis.)

Indication of Current Direction in Diagrams

To characterize the...

Friction Force Fundamentals

Friction, as a contact force, is a force applied by a surface to an object in contact with it. The frictional force is always parallel to the surface, while the contact force (or normal force) is always perpendicular to the surface itself. Friction acts to oppose any externally applied force.

The vector sum of the contact force (Fc) and the friction force (Ff) represents the total force exerted by the surface on the object. There exists a maximum value for the magnitude of the friction force (Ff). If an applied force (Fa) exceeds this maximum value, it cannot be countered by the frictional force, and the block will begin to move. (Note: The contact force (Fc) also has a maximum value, beyond which the surface itself...

Fundamentals of Light Propagation

• The light propagates in a straight line in transparent and homogeneous media.
• The speed of light is approximately 300,000 km/s.

Refractive Index

The absolute refractive index of a substance is the ratio between the speed of light in a vacuum and its speed through the substance, represented by the letter n.

Laws of Reflection

• When light reflects off a specular surface, the incident ray, the reflected ray, and the normal lie in the same plane (first law of reflection).
• The angle of reflection equals the angle of incidence (second law of reflection).
• Images formed in flat mirrors are virtual, upright, and the same size as the object.

Spherical Mirrors

A spherical mirror is a portion of a sphere:

• When the inside of the cap

Understanding Voltage and Potential Difference

Voltage: The voltage that a generator is capable of providing is the energy transferred to each coulomb of charge to traverse the circuit. It is represented by the letter V and is measured in volts.

One volt (V) is equal to one joule per coulomb. That is, a generator of 220 volts, for example, is capable of providing an energy of 220 joules to each coulomb of charge. The formula is: 1 volt = 1 joule / 1 coulomb.

Current Intensity and Amperes

Current intensity: The intensity of an electrical current is defined as the amount of electric charges passing through a section of the conductor in a given time. This quantity is represented by the letter I, and is measured in amperes.

One ampere (A) equals one...

The Earth in the Universe

Historically, the geocentric model placed our planet at the center of the universe, whereas the heliocentric theory established the Sun as the center.

Distances in the Universe

• Astronomical Unit (AU): The average distance between Earth and the Sun, equivalent to approximately 149,600,000 km to 150,000,000 km.
• Light-year: The distance light travels in one year at a speed of 300,000 km/s.

The Known Universe: Galaxies

Galaxies are defined as large clusters of stars, gas, and dust. They can contain billions or trillions of stars, which often host planetary systems.

Components of Galaxies

• Nebulae: Concentrations of interstellar gas (hydrogen and helium) and dust.
• Star Clusters: Compact groups of stars. When they are very dense,

Kinematics and Motion

• Path: The line that describes the motion of an object.
• Displacement: The straight-line distance between the object's initial and final positions.
• Scalars: Quantities that only require a number and a unit, such as temperature, distance, time, and mass.
• Vectorial Magnitudes: Quantities that require a number, unit, direction, and sense, such as velocity and force.

Vector Components

• Origin: The end of the vector not bearing the arrow.
• Line of Action: The line on which the vector is located.
• Direction: Indicated by the arrow.

Types of Motion

• MRU (Uniform Rectilinear Motion): Movement where the trajectory is a straight line and speed is constant.
• Accelerated Movement: Movement where speed varies over time.
  • Case 1: If speed increases, acceleration

Force is a physical quantity that can cause a body to deform or change its state of motion (start moving, stop, or change direction). As a vector quantity, force has both magnitude and direction. Its magnitude is measured in Newtons (N) within the International System of Units (SI).

Characteristics of a Force

Since force is a vector quantity, to fully define its characteristics, we need to know:

• Application Point: This is the specific point on the body where the force is applied. It represents the origin of the force vector.
• Magnitude (or Intensity): This is the numerical value indicating the strength of the force, measured in Newtons. It corresponds to the length of the force vector.
• Sense: This indicates the specific direction along the line of

Fluid Pressure and its Effects

A fluid exerts pressure in all directions on a body immersed in it (P = d * h * g). The magnitude increases with depth. The pressure does not depend on the area. If h is the same, the pressure will be the same. But the force depends on the area. The force of the water at the bottom of a lake is greater than that exerted in a pool (F = P * A). The pressure exerted by a liquid also depends on its density. If the liquid in Torricelli's experiment had been any other than mercury and of lower density, the column would have increased.

Bathysphere: A spherical steel tank used for underwater observations, supported by a cable from a ship.

States of Matter

• Solid: Molecules are linked by very strong cohesion and have a definite

Fundamental Principles of Light Reflection

Specular Reflection: This occurs when light comes in the form of parallel rays impinging on a flat and very smooth surface.

Diffuse Reflection: This happens when the surface is rough and light is shot out in all directions.

Fermat's Principle: Fermat's principle is the geometric form of expressing the law of reflection.

Mirrors and Geometric Optics

Plane Mirror: In a plane mirror, incident and reflected rays form the same angle with respect to an imaginary line perpendicular to the surface.

Characteristics of Curved Mirrors

Curved Mirrors: When a ray of light reaches a point of curvature of the mirror, it forms an angle with the normal (N). There are two types of curved mirrors:

• Concave: These curve inward