Untitled Flashcard Set
Newton’s Three Laws of Motion
Isaac Newton developed three laws that explain how forces affect the motion of objects.
1. Law of Inertia — Newton’s First Law
The Law of Inertia states that an object at rest will remain at rest, and an object in motion will continue moving at a constant velocity unless acted upon by an external unbalanced force.
Mass and Inertia
Inertia is an object's resistance to a change in its motion. In general, the greater an object's mass, the greater its inertia.
For example:
A loaded truck has more inertia than a bicycle.
It takes more force to change the motion of the truck.
A book resting on a table stays at rest because there is no unbalanced force causing it to move.
Balanced and Unbalanced Forces
Balanced forces are equal in magnitude and opposite in direction. They produce a net force of zero, so they do not change an object's motion.
Unbalanced forces produce a nonzero net force. They can cause an object to:
Speed up
Slow down
Change direction
Start moving
Stop moving
For example, kicking a soccer ball applies an unbalanced force that changes the ball's motion.
2. Law of Acceleration — Newton’s Second Law
Newton's Second Law of Motion states that the acceleration of an object depends on the net force acting on it and its mass.
The relationship is expressed as:
F = ma
Where:
F = net force, measured in newtons (N)
m = mass, measured in kilograms (kg)
a = acceleration, measured in meters per second squared (m/s²)
This means that a greater force produces greater acceleration when mass stays the same. If the force stays the same, an object with greater mass will have less acceleration.
Example: Pushing an empty shopping cart requires less force to accelerate it than pushing a heavily loaded shopping cart.
3. Law of Interaction — Newton’s Third Law
Newton's Third Law of Motion, also called the Law of Interaction, states:
For every action force, there is an equal and opposite reaction force.
Forces always occur in pairs and act on different objects.
Example: When you push against a wall, you exert a force on the wall, and the wall exerts an equal and opposite force on you.
Other examples include:
A swimmer pushes water backward, and the water pushes the swimmer forward.
A rocket pushes gases downward, and the gases push the rocket upward.
When you jump, your feet push the ground downward, while the ground pushes you upward.
Force
is a push or pull acting on an object.
can cause an object to accelerate, change direction, or deform.
is a vector quantity, meaning it has both magnitude and direction.
Measure: newtons (N)
Types of Forces
Contact Force
occurs when two objects physically touch each other.
Examples:
Friction
Pushing a box
Pulling a rope
Air resistance
Non-Contact Force
also called a field force, acts on an object without the objects physically touching.
Examples:
Gravity
Magnetic force
Electric force
Newton’s Law of Acceleration
Acceleration
rate at which an object changes its velocity.
vector quantity, which means it has both magnitude and direction.
An object accelerates when it:
Speeds up
Slows down
Changes direction
Acceleration as a Change in Speed or Direction
A change in speed produces acceleration. For example, a car accelerating from a stop is experiencing acceleration.
A change in direction also produces acceleration, even when the speed stays constant. For example, a car turning around a corner experiences centripetal acceleration.
The Relationship Among Force, Mass, and Acceleration
Newton's Second Law of Motion, also called the Law of Acceleration, describes the relationship between force, mass, and acceleration.
The formula is:
F = ma
Where:The law states that the acceleration of an object is directly proportional to the net force acting on it and inversely proportional to its mass.
F = Force, measured in newtons (N)
m = Mass, measured in kilograms (kg)
a = Acceleration, measured in meters per second squared (m/s²)
Direct Proportionality Between Force and Acceleration
When the mass of an object remains constant, increasing the force increases its acceleration.
More force → More acceleration
For example, pushing a shopping cart harder causes it to accelerate more quickly.
Inverse Proportionality Between Mass and Acceleration
When the applied force remains constant, increasing the mass decreases the acceleration.
More mass → Less acceleration
For example, an empty shopping cart accelerates more easily than a heavily loaded shopping cart when the same force is applied.
Solving a Word Problem
Problem
A force of 15.6 N causes an object to accelerate at 3.0 m/s². Find the mass.
Given
F = 15.6 N
a = 3.0 m/s²
m = ?
Formula
Starting with:
F = ma
Solve for mass:
m = F/a
Solution
m = 15.6 N ÷ 3.0 m/s²
m = 5.2 kg
Answer
The mass of the object is 5.2 kg.
Newton’s Law of Interaction
Newton's Third Law of Motion, also known as the Law of Interaction, states:
For every action force, there is an equal and opposite reaction force.
Whenever one object exerts a force on another object, the second object simultaneously exerts a force of equal magnitude and opposite direction on the first object.
Common Misconception
A common misunderstanding is that the action and reaction forces cancel each other out.
They do not cancel each other because they act on different objects.
For example, when a person jumps from a boat:
The person pushes the boat backward.
The boat pushes the person forward.
Both the person and the boat move in opposite directions.
Their accelerations can be different because their masses are different, and other forces may also act on them.
Examples of the Law of Interaction
1. Walking
When you walk, your foot pushes the ground backward. The ground then pushes your foot forward with an equal and opposite force.
This reaction force helps move you forward.
2. Bouncing a Ball
When a ball hits the ground, the ball exerts a force downward on the ground.
The ground exerts an equal and opposite force upward on the ball, causing the ball to bounce.
3. Flight of a Bird
A bird's wings push air downward.
The air exerts a force upward on the bird, helping the bird fly.
ELECTRICITY AND CIRCUITS
I. What Is Electricity?
Electricity is the movement or flow of electric charge.
Protons → positively charged (+)
Electrons → negatively charged (−)
Electric current → flow of electric charge, mainly electrons in a metal conductor
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II. Electrical Conductors
Conductors
materials that allow electricity to flow easily.
This is because they have electrons that can move freely.
Examples:
Copper, Aluminum, Silver, Gold
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III. Electrical Insulators
Insulators
materials that do not allow electricity to flow easily because their electrons are not free to move.
Examples:
Rubber, Plastic, Glass, Dry wood
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IV. What Is a Circuit?
Circuit
complete pathway through which electric current flows.
Four components:
Power source – provides electrical energy
Conducting path – provides a path for current
Load – uses electrical energy
Control – controls the flow of electricity
Example:
Battery → Wire → Switch → Light bulb → Wire → Battery
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V. Components of a Circuit
Power Source
provides electrical energy to the circuit.
A battery has:
Positive terminal (+)
Negative terminal (−)
The battery provides voltage, which drives current through the circuit.
Example: Battery, Generator, Solar cell
Conducting Path
the path through which electric current flows.
Usually made from: Copper, Aluminum
These materials are good conductors because they have low resistance and high conductivity.
Load
uses electrical energy to perform a function.
Examples:
Light bulb, Motor, Resistor, Heater, Buzzer
A resistor helps limit or control current and converts electrical energy into heat.
A light bulb converts electrical energy into light and heat.
Control
manages the flow of electricity.
The most common control is a switch.
ON → Closed circuit → Current flows
OFF → Open circuit → Current stops
Types of switches: Toggle switch, Push-button switch, Rotary switch
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Closed Circuit
complete path for current to flow.
Open Circuit
has a broken or incomplete path. Therefore, current cannot flow.
Causes: Switch is OFF, Broken wire, Disconnected component
Open = Current does not flow
Short Circuit
occurs when current takes an unintended low-resistance path, bypassing the normal components.
Causes: Bare wires touching, Damaged insulation, Incorrect connections
Dangers: Excessive current, Overheating, Sparks, Damage to components, Fire
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Current
flow of electric charge through a conductor.
Unit: Amperes (A)
Voltage
electric potential difference between two points.
It provides the "push" that drives current through a circuit.
Unit: Volt (V)
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Series Circuit
A series circuit has components connected in a single path.
Characteristics:
Only one path for current
Same current flows through all components
Voltage is divided among components
If one component breaks, the whole circuit may stop working
Advantages:
Simple design
Easy to build
Requires less wiring
Disadvantages:
One broken component can stop the entire circuit
Voltage is divided among loads
Components cannot easily be controlled independently
Parallel Circuit
A parallel circuit has multiple paths or branches for current.
Each load is connected across the same two points of the power source.
Characteristics:
Multiple paths for current
Current is divided among branches
Voltage across each branch is equal to the source voltage
If one branch fails, other branches can continue working
Advantages:
Devices can operate independently
Each component receives the full supply voltage
One broken bulb does not necessarily turn off the others
Disadvantages:
Requires more wires
More complicated to build
Can cost more
More branches increase the total current drawn
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ELECTRICAL SAFETY
I. Common Electrical Hazards
Overloading and Inadequate Wiring
Overloading happens when too many devices are connected to one circuit.
This causes excessive current, which can:
Overheat wires
Damage equipment
Cause electrical fires
Proper circuit design helps prevent overloading.
Damaged Equipment and Components
Damaged wires, appliances, plugs, and exposed conductors can cause:
Electric shock
Electrical fires
Short circuits
Deteriorated insulation may expose live wires and increase the risk of accidents.
Improper Electrical Installation
Faulty wiring and damaged insulation can cause:
Electric shock
Overheating
Short circuits
Fires
Wet environments increase electrical risks because water conducts electricity.
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II. Potential Injuries and Accidents
Electric Shock
Muscle Contractions
Causes involuntary muscle spasms.
May make it difficult for a person to release the electrical source.
Can result in prolonged exposure and injury.
Cardiac Arrest
Electrical current can disrupt the heart's rhythm.
May lead to cardiac arrest and death.
Respiratory Failure
Electric shock can interfere with breathing.
Severe shock may cause respiratory arrest.
Electrical Burns
Arc Flash Burns
Caused by extremely hot plasma produced by an electrical arc between conductors.
Can cause severe tissue damage.
Thermal Contact Burns
Occur when skin directly touches a hot electrical conductor.
Falls and Other Injuries
Electric shock can cause muscle contractions that may result in:
Falls from heights
Falls into machinery
Head injuries
Other physical trauma
Loss of consciousness can make injuries more severe.
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III. Electrical Fires
Ways to Prevent Electrical Fires
Avoid overloading circuits — Do not connect too many devices to one circuit.
Inspect wiring — Check for frayed, damaged, or exposed wires.
Replace faulty appliances — Repair or discard damaged equipment.
Keep electrical equipment away from heat — Heat can damage insulation and increase fire risks.
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IV. Electrical Safety Devices
Fuses
protects a circuit from excessive current.
Its metal wire melts when the current becomes too high.
This interrupts the flow of electricity and prevents damage.
A blown fuse must be replaced.
Circuit Breakers
automatic safety switch.
It stops electricity when the current becomes too high.
It helps:
Protect electrical systems
Prevent equipment damage
Reduce the risk of electrical fires
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V. Earthing and Grounding
Earthing
Connects an electrical system to the Earth.
Helps stabilize voltage.
Provides a low-resistance path for fault current.
Reduces the risk of electric shock.
Grounding
Connects electrical systems to Earth.
Helps:
Protect equipment
Stabilize voltage
Balance electrical loads
Prevent electric shocks
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VI. Safety Precautions and Preventive Measures
Proper Use of Outlets and Cords
Do not overload electrical outlets.
Avoid connecting too many appliances or adapters to one outlet.
Use power strips with surge protectors when appropriate.
Keep cords and plugs in good condition.
Regular Inspection and Maintenance
Inspect Regularly
Check:
Cords
Plugs
Appliances
Connections
Look for:
Frayed wires
Loose connections
Damaged insulation
Other signs of wear
Replace damaged parts immediately.
Professional Audits
Have qualified professionals inspect electrical systems.
Professional inspections can:
Identify hazards
Ensure safety compliance
Maintain system reliability
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VII. Emergency Protocols
Electrical Shock
What to do:
Do NOT touch the person directly while they may still be in contact with electricity.
Turn off the power source.
Switch off the circuit breaker, or unplug the appliance if it is safe to do so.
Once the area is safe, call emergency services.
Give first aid/CPR if trained and appropriate.
Electrical Fire
What to do:
Use a Class C-rated fire extinguisher for an energized electrical fire.
Never use water on an electrical fire because water can conduct electricity.
If the fire cannot be controlled safely:
Evacuate the area.
Call the fire department/emergency services.
Current, Voltage, and Resistance
1. Current Electricity
Current electricity is the continuous flow of electric charge, usually through a conductor such as a metal wire. In metal wires, the moving charges are primarily electrons.
Unlike static electricity, which involves accumulated electric charge, current electricity involves a continuous flow of charge through a circuit.
2. Electric Current
Electric current is the rate at which electric charge flows through a conductor.
Current is measured in amperes (A), named after André-Marie Ampère .
Flow of Electrons
In a metal conductor:
Electrons move from the negative side toward the positive side.
Conventional current is considered to flow from positive to negative.
The conventional-current direction is used in most circuit diagrams and electrical calculations.
Measuring Current
An ammeter measures electric current in amperes (A).
An ammeter must be connected in series with the circuit.
This means the current must pass through the ammeter so that it can measure the current flowing through the circuit.
3. Voltage
Voltage, also called electric potential difference, is the difference in electrical potential energy per unit charge between two points.
Voltage provides the energy that drives electric charge through a circuit.
Voltage is measured in volts (V).
Water Analogy
Voltage can be compared to water pressure:
Voltage → water pressure
Current → flow of water
Resistance → restriction to water flow
For example, a 9 V battery provides a greater potential difference than a 1.5 V battery.
Voltage Sources
Voltage sources provide electrical energy to a circuit.
Examples include:
Batteries
Power supplies
Generators
Electrical power stations
Measuring Voltage
A voltmeter measures voltage in volts (V).
A voltmeter is connected in parallel across the component or points where the voltage is being measured.
4. Resistance
Resistance is the opposition to the flow of electric current.
Resistance is measured in ohms (Ω).
A resistor is a component designed to provide a specific amount of resistance and control current in a circuit.
There are two common types:
Fixed resistor — has a fixed resistance value.
Variable resistor — allows its resistance to be adjusted, such as a potentiometer.
Factors Affecting Resistance
The resistance of a conductor depends on several factors.
1. Material
Different materials have different electrical resistance.
Copper and silver have relatively low resistance and are good conductors.
Rubber and glass have very high resistance and are insulators.
2. Length
A longer conductor generally has greater resistance because electrons have a longer path through the material.
Longer wire → Greater resistance
3. Cross-Sectional Area
A thicker conductor generally has lower resistance because there is more space for charge to flow.
Thicker wire → Lower resistance
4. Temperature
For most metallic conductors, resistance increases as temperature increases.
As temperature rises, the atoms in the material vibrate more, increasing the interactions that impede electron movement.
Measuring Resistance
An ohmmeter measures electrical resistance in ohms (Ω).
When measuring resistance with an ohmmeter, the circuit should be turned off and disconnected from its power source.
Resistor Color Codes
Resistors often use colored bands to indicate their resistance value and tolerance.
For a common 4-band resistor:
First band = first digit
Second band = second digit
Third band = multiplier
Fourth band = tolerance
Color Code
Example: Reading a Resistor
Suppose a resistor has four bands:
Red – Violet – Orange – Gold
Step 1: First digit
Red = 2
Step 2: Second digit
Violet = 7
So the first two digits are:
27
Step 3: Multiplier
Orange = ×1,000
Therefore:
27 × 1,000 = 27,000 Ω
or
27 kΩ
Step 4: Tolerance
Gold = ±5%
Therefore, the resistor is:
27,000 Ω ±5%
The possible resistance range is:
Minimum: 25,650 Ω
Maximum: 28,350 Ω
So the actual resistance can be between 25,650 Ω and 28,350 Ω.
Relationship Between Current, Voltage, and Resistance
These three quantities are connected by Ohm's Law:
V = IR
Where:
V = voltage in volts (V)
I = current in amperes (A)
R = resistance in ohms (Ω)
From this equation:
I = V/R
and
R = V/I
Simple Summary
Ohm’s Law
Ohm’s Law describes the relationship between voltage, current, and resistance in an electrical circuit. It is named after German physicist Georg Simon Ohm.
The three quantities
Voltage (V) — the electrical pressure that pushes current through a circuit. It is measured in volts (V).
Current (I) — the flow of electric charge. It is measured in amperes (A).
Resistance (R) — how much a component opposes the flow of current. It is measured in ohms (Ω).
The three forms of Ohm’s Law
You can rearrange the formula depending on what you need to find:
Voltage: V = I × R
Current: I = V ÷ R
Resistance: R = V ÷ I
How it works
If resistance stays the same:
Higher voltage → higher current
Lower voltage → lower current
If voltage stays the same:
Higher resistance → lower current
Lower resistance → higher current
Worked example
Suppose a circuit has:
Voltage = 15 V
Resistance = 3 Ω
To find the current:
I = V ÷ R
I = 15 ÷ 3
I = 5 A
So, the current flowing through the circuit is 5 amperes.
Ohm’s Law in everyday life
Ohm’s Law helps explain how many electrical devices and circuits behave, including:
Chargers — electrical resistance affects current flow.
Light bulbs — resistance and current affect how electrical energy is converted into light and heat.
Air conditioners — voltage, current, and the resistance/impedance of electrical components are related.
Electromagnetic Waves
1. What is electromagnetic radiation?
Electromagnetic radiation (EMR) is a form of energy that travels through space as electromagnetic waves.
An electromagnetic wave consists of:
Electric field — oscillates in one direction.
Magnetic field — oscillates perpendicular to the electric field.
Direction of propagation — the direction in which the wave travels, perpendicular to both fields.
Because the electric and magnetic fields are perpendicular to the direction of travel, electromagnetic waves are transverse waves.
Unlike mechanical waves, electromagnetic waves do not need a material medium. They can travel through a vacuum, such as outer space.
2. Historical development
Isaac Newton — Corpuscular Theory
Newton proposed that light was made of tiny particles called corpuscles.
His theory could explain:
Reflection
Refraction
However, it could not adequately explain diffraction and made an incorrect prediction about the speed of light in different materials.
Christiaan Huygens — Wave Theory
Huygens proposed that light behaves as a wave.
His theory helped explain:
Diffraction
Interference
This provided important evidence for the wave nature of light.
Luminiferous ether
In the 19th century, scientists proposed the existence of the luminiferous ether, a hypothetical medium that they thought was necessary for light to travel through space.
Michelson–Morley Experiment
The Michelson–Morley experiment attempted to detect Earth's motion through the supposed ether.
They expected to observe a difference in the speed of light depending on its direction. However, they found no significant change in the interference pattern.
This result provided strong evidence against the ether hypothesis and supported the idea that light does not require such a medium.
James Clerk Maxwell
theory of electromagnetism and showed mathematically that changing electric and magnetic fields can propagate as waves.
He concluded that light is an electromagnetic wave.
His work is summarized by Maxwell's equations.
Heinrich Hertz
In 1887, Heinrich Hertz experimentally generated and detected electromagnetic waves, providing experimental confirmation of Maxwell's predictions.
3. Parts and characteristics of an electromagnetic wave
Electric field
The electric field oscillates in one direction and is part of the electromagnetic wave.
Magnetic field
The magnetic field oscillates perpendicular to the electric field.
Direction of propagation
This is the direction in which the electromagnetic wave carries energy.
Amplitude
The amplitude is the maximum strength of the electric or magnetic field measured from its equilibrium position.
Greater amplitude generally means greater intensity.
Equilibrium position
The equilibrium position is the central or undisturbed position around which the fields oscillate.
Wavelength (λ)
Wavelength is the distance between corresponding points on consecutive waves, such as crest-to-crest.
It is measured in meters (m).
Frequency (f)
Frequency is the number of complete wave cycles passing a point each second.
It is measured in hertz (Hz).
4. Wavelength, frequency, and energy
These three quantities are closely related.
The relationship between wavelength and frequency is:
c = fλ
Therefore:
f = c/λ
and
λ = c/f
where:
c = speed of light = 3.00 × 10⁸ m/s
f = frequency in Hz
λ = wavelength in meters
The relationship between energy and frequency is:
E = hf
where:
E = energy in joules (J)
h = Planck's constant = 6.63 × 10⁻³⁴ J·s
f = frequency in Hz
5. Worked Example 1: Finding Frequency
Question
A radio wave has a wavelength of 2.00 m. What is its frequency?
Given
c = 3.00 × 10⁸ m/s
λ = 2.00 m
Required
f = ?
Equation
f = c/λ
Solution
f = (3.00 × 10⁸)/(2.00)
f = 1.50 × 10⁸ Hz
Answer
1.50 × 10⁸ Hz
6. Worked Example 2: Finding Wavelength
Question
What is the wavelength of an electromagnetic wave with a frequency of 7.50 × 10¹⁴ Hz?
Given
c = 3.00 × 10⁸ m/s
f = 7.50 × 10¹⁴ Hz
Required
λ = ?
Equation
λ = c/f
Solution
λ = (3.00 × 10⁸)/(7.50 × 10¹⁴)
λ = 4.00 × 10⁻⁷ m
Answer
4.00 × 10⁻⁷ m
This is also 400 nm, which falls within the visible-light region.
7. Electromagnetic Spectrum
The electromagnetic spectrum is the complete range of electromagnetic waves.
From lowest frequency/energy and longest wavelength to highest frequency/energy and shortest wavelength:
Radio waves
Microwaves
Infrared
Visible light
Ultraviolet
X-rays
Gamma rays
Radio waves
Longest wavelengths
Lowest frequencies and energies
Used in radio and television broadcasting, communication, and radar
Microwaves
Shorter wavelengths than radio waves
Higher frequencies than radio waves
Used in microwave ovens, satellite communication, radar, and Wi-Fi
Infrared (IR)
Associated with thermal radiation and often experienced as heat
Longer wavelengths than visible red light
Used in remote controls, thermal cameras, and some night-vision systems
Visible light
The portion of the electromagnetic spectrum detectable by the human eye
Includes colors from red to violet
Used in lighting, photography, optical instruments, and vision
Ultraviolet (UV)
Higher frequency and energy than visible light
Can cause skin damage with excessive exposure
Used for sterilization, detecting substances, and curing certain materials
X-rays
Very short wavelengths
High frequencies and energies
Can pass through soft tissue more easily than dense materials such as bone
Used in medical imaging and security scanning
Gamma rays
Shortest wavelengths
Highest frequencies
Highest photon energies
Used in applications such as cancer radiation therapy and sterilization