Communication notes Flashcards
What is a common way to transmit energy from one location to another?
A common way to transmit energy from one location to another is via a wave.
What is a wave?
A wave is where energy is moved from one location to another, but the particles in between have no overall movement.
Can energy be transmitted without moving any matter?
Energy can also be transmitted without moving any matter.
What are the two categories of waves?
Mechanical (require a medium), and
Electromagnetic (DO NOT require medium).
What is the amplitude of a wave?
The amplitude ( ) of a wave is the distance from the centre line (or the still position) to the top of a crest or to the bottom of a trough .
What is the amplitude measured in?
It is usually measured in metres, m and has the symbol, a.
What is wavelength?
Wavelength is like the distance between two adjacent peaks or two adjacent troughs.
Or, wavelength is the time required to complete one full cycle of the wave.
What is wavelength measured in?
It is usually measured in metres, m and has the symbol, λ (lamda).That is, how many wavelengths per second.
What is the frequency of a wave?
Frequency is the number of wave cycles passing a point per unit time.
A higher frequency means a shorter wavelength, and a lower frequency means a longer wavelength.
What is the formula of OHM’s Law?
V=IR
What does ‘V’ stand for in Ohm’s law?
V=Voltage
What does ‘I’ stand for in Ohm’s law?
I=Current
What does ‘R’ stand for in Ohm’s law?
R=Resistance
What is Ohm’s law?
Ohm’s law is the formula that shows the relationship between voltage, current and resistance.
What is the ‘current’ in a circuit?
the amount of energy carriers passing a particular point
It is measured in Amperes (A)
Also stands for ‘I’ in OHMS LAW
What is the ‘voltage’ in a circuit?
the amount of energy that the current is carrying; the potential difference (or the difference in electrical energy) between two points
It is measured in volts.
Stands for ‘V’ in OHMS LAW.
What is the ‘resistance’ in a circuit?
Everything that resists or opposes the flow of electrons in a circuit.
Measured in OHMS.
Srands for ‘R’ in OHMS law.
How do electrons flow in a circuit?
Electrons flow from positive to negative terminals.
What are the rules/formulas for a series circuit?
RT=R1+R2+R3…..
IT=I1=I2=I3(Current is constant)
VT=V1+V2+V3
What are the rules/formulas for a parallel circuit?
VT=V1+V2+V3 (Voltage is constant)
IT=I1+I2+I3
1/RT=1/R1+1/R2+1/R3
What is a combination circuit and how do you solve it?
A combination circuit is one that has a “combination” of series and parallel paths for electricity to flow.
To solve you need to apply the rules to “condense” all the resistors down to one equivalent resistor.
What are the two main ways energy can be classified?
Kinetic and potential
Which way does electrons flow in a circuit?
They flow opposite to the current (positive to negative). The electrons flow from positive terminals to negative.
What are atoms made up of?
Protons, neutrons and electrons.
The flow of electrons through a wire is known as?
The current, otherwise known as electricity.
Finish the sentence. If you increase the voltage in a circuit the…
Current increases or resistance.
What does low resistance mean?
Low resistance means the electrons are freer to move so it conducts more. e.g. copper, silver
Insulators have a high resistance which means that the electrons are not free to move. e.g. rubber, plastic, cloth, glass.
Finish the sentence. If you increase the resistance you…
decrease the current
What are the Three things are required in order to have an electric circuit:
Power supply – this provides the electrical energy needed.
Load – this is what converts or changes the electrical energy into another form.
For example, a globe converts electrical energy into light (and heat), a kettle jug converts the electrical energy into heat.
Conducting pathway – enables the current to flow (or move) around the circuit.
What happens when you turn on the switch in a circuit?
When you turn on a switch, you are actually completing the circuit and allowing the electrons to flow!
What is a series circuit?
A series circuit is a circuit in which resistors are arranged in a chain, so the current has only one path to take. The current is the same through each resistor. (M)
What is a parallel circuit?
A parallel circuit is defined as one where all components are connected between the same set of electrically common points. The current is different for each pathway. (M)
What is a combination circuit?
A combination circuit is one that has a “combination” of series and parallel paths for the electricity to flow.
What happens if there is a fault/break in a series circuit?
Current will stop flowing around the circuit if there is a break at any point.
What is constant in a series circuit?
The same current passes through all components.
If the wire leading to the other is broken in a parallel circuit what happens?
The current will continue to flow through one bulb if the wire leading to the other is broken.
What is constant in a parallel circuit?
Voltage-Each resistor has the same voltage
What is a voltmeter?
Measures the voltage in an electrical circuit. You hook up the voltmeter parallel to the resistor.
What is an ammeter?
The ammeter measures the current.
You hook up the ammeter in series to the resistor.
What are the two categories of waves?
Mechanical (require a medium), and
Electromagnetic (DO NOT require medium).
There are two basic types of wave motion:
longitudinalwaves, and
transversewaves.
What is a longitudinal wave?
In a longitudinal wave the particle displacement is parallel to the direction of wave propagation.
The wave is seen as the motion of the compressed region, which moves from left to right.
For example, sound waves.
What is a transverse wave?
In a transverse wave the particle displacement is perpendicular to the direction of wave propagation.
These are what you typically think of when you hear the word ‘wave’.
For example, light waves.
How do longitudinal waves move?
particles move backwards and forwards in the same direction of the wave
what is the medium in a wave?
The material through which a wave travels.
The more elastic the particles are in a mechanical wave the…..
further, the wave travels
which wave requires a medium to transmit? (Mechanical or a transverse wave?)
Mechanical transverse waves pass perfectly through a solid medium but not a liquid or a gas medium (as particles cannot return to their original position).
Transverse waves travel at right angle to the direction of energy transfer
The particles move up and down
Electromagnetic (EM) waves do not require a medium to transmit – they can, therefore, move through an empty space (a vacuum)
What can the human eye see on the EMS spectrum?
The human eye can only detect only a small portion of this spectrum called visible light.
So how are magnetism and electricity connected?
Flowing electrons produce a magnetic field, and spinning magnets cause an electric current to flow.
Electromagnetism is the interaction of these two important forces.
The region around a magnet where magnetic effects can be experienced is called the
magnetic field.
Faraday’s Three Rules for Magnetic Field Lines
Each magnetic field line is a continuous loop that leaves the north end of the magnet, enters at the south end and passes through the magnet back to the north end.
Field lines do not intersect.
The closeness of the magnetic field lines represents the strength of the magnetic field.
What is a solenoid?
A solenoid (a cylindrical coil of copper wire) can produce a magnetic field similar to a bar magnet.
What happens if you place a core (usually a piece of iron) in the middle of a solenoid?
If we place a core (usually a piece of iron) in the middle of the solenoid, then we can increase the magnetic field and produce an electromagnet
What is an electromagnet?
An electromagnet is a type of magnet in which the magnetic field is produced by an electric current. The magnetic field dissapears when the current is turned off. Electromagnets usally consist of wire wound into a coil.
What is a permanent magnet?
A permanent magnet is an object made from material that is magnetized and creates its own persistent magnetic field. An everyday example is a refrigerator magnet used to hold notes on a refrigerator door.
How do magnets generate electricity?
When a magnet is moved inside a coil of wire, it causes the electrons in the atoms inside the wire to move.
The moving electrons in the wire create an electric current!
This current is alternating current (AC) as it changes direction
What is a simple electric motor?
These work opposite to a generator.
When the current flows through the coil of wire, it interacts with the magnetic field and the coil spins.
What does the magnet’s speed in and out of the solenoid have on the current?
It affects the current being generated. The faster the magnet moves in and out of the solenoid, the greater the current on the ammeter.
Does any current flow when the magnet is still within the solenoid?
When the magnet is still in the solenoid, no current was generated on the ammeter.
Does changing the Pole (north or south) that approaches the solenoid to have an effect?
Yes. It changes the directions of the current.
Can you suggest what you could change to induce more current?
- Increase the number of turns of wire in the coil. The more coils the more current induced.
- The faster you move the magnet in and out of the solenoid the greater the current.
- Increasing the strength of the magnetic field. With a stronger magnetic field, a bigger current is induced due to more lines of force to cut.
How have advances in knowledge of the electromagnetic spectrum impacted our society?
Everyday life is pervaded by artificially made electromagnetic radiation: Food is heated in microwave ovens, airplanes are guided by radar waves, television sets receive electromagnetic waves transmitted by broadcasting stations, and infrared waves from heaters provide warmth.
How can the interaction of magnets be explained?
The interaction of magnets can be explained by a field model
What are magnets used for?
Magnets are used in the generation of electricity and the operation of motors.
velocity/speed
Is calculated by wavelength times frequency
- Imagine you are creating a public service video warming people of the dangers of ultraviolet light. What important information would you need to get across to people? Include tips for protecting the skin from ultraviolet light.
Ultraviolet light or lamps can cause the following issues:
• Skin cancer: UV radiation is the main cause of skin cancer.
• Eye damage: UV radiation can damage the cornea and retina, and can cause cataracts.
• Suppression of the immune system: Exposure to UV radiation can decrease the body’s ability to fight off infections.
• Premature aging: UV radiation can cause premature wrinkles, age spots, and dryness of the skin.
To protect yourself from the dangers of ultraviolet light: wear sunglasses and longsleeves when outdoors; choose a good sunscreen that protects you from UV rays; stay out of the sun when possible - especially between the hours of 12 pm - 3 pm when the UV rays at their strongest.
How are X rays and gamma rays used in medicine?
X-rays contain enough energy to penetrate through soft tissue but are not strong enough to penetrate through hard bone. Medical x-rays are used to generate images of tissues and structures inside the body. If x-rays traveling through the body also pass through an x-ray detector on the other side of the patient, an image will be formed that represents the “shadows” formed by the objects inside of the body.
Gamma rays possess they highest amount of energy. This means that they can penetrate down into our DNA. They can be used to kill cancers cells or to sterilise equipment by killing bacteria and other organisms that may be on them.
Describe how wave frequency changes across the electromagnetic spectrum, from radio waves to gamma rays.
Frequency is inversely proportional to the wavelength. That is, as the wavelength decrease then the frequency will increase. As we move from radio waves (long wavelength and low frequency) across to gamma rays (short wavelength and high frequency) the wavelength decrease and the frequency increases (along with the energy that the waves possess).
What is the electromagnetic spectrum (EMS)?
The electromagnetic (EM) spectrum is the range of all types of electromagnetic radiation. From long radio waves through to gamma rays, which has the highest energy.
What are three uses of radio waves?
AM and FM radios
police radar
GPS
ultraviolet ray
10^-8m - Emitted from the sun and can cause skin cancer
X ray
10^-10m - Used from medical imaging
infarared
10^-5m or 0.01 mm - Used for remote controls, optical fibers and monitoring temperature.
microwave
10^-2m or 1cm - used for communication and cooking food
Radio wave
1m-10^4m - used mainly for communcations
Gamma ray
10^-15m - used to treat or diagnose cancers
Visible light
10^-7m- allows us to see and used for photography
compare the brightness of parallel and series
It is brighter in parallel because it receives the full voltage from the battery while in series, the voltage is shared.
compare the brightness of parallel and series
- Can I identify the movement of energy and particles in transverse and longitudinal waves?
a. Transverse: particles move perpendicular (up and down) to the direction of the wave
Longitudinal: particles move backwards and forwards in the same direction of the wave
- Can I explain why red is always on top of a rainbow and violet is on the inside?
Red light has the longest wavelength and will bend the least.
Violet light has the shortest wavelength and will bend the most.
- Can I state the relationship between voltage, resistance and current in a circuit?
As voltage increases, so does current or resistance.
- Can I compare a series circuit to a parallel circuit?
HINT: Think pathways, current, voltage and resistance.
In a series circuit:
• The same current flows through all components in the circuit.
• There is ONE pathway for the current to travel.
• Different potential difference (voltage) exist across each component.
In a parallel circuit:
• Different current flows through each component in the circuit.
• There are multiple pathways for the current to travel.
• The potential difference (voltage) existing across the various component in the circuit is same.
Can I explain why an ammeter and voltmeter need to be connected as shown in the diagram below?
Voltage is the difference in electrical energy between two point so it needs to be connected in PARALLEL to work out the difference in the energy going into the load and what’s coming out. That is, the energy that has been used by the component.
However, current needs to be connected needs to be connected in SERIES so that all energy carriers passing through the load/electrical component also pass through the ammeter.
What is a solenoid? What is the purpose of using an iron core in a solenoid?
A solenoid is a tightly wound coil of wire (usually copper) that acts as a magnet when carrying electric current.
Why does a horseshoe magnet have a stronger attractive power than a bar magnet?
This is because the magnetic field lines are closer together, making the magnet stronger. REFER DIAGRAM BELOW.
Can I explain the relationship between wavelength and frequency?
The shorter the wavelength, the higher the frequency the energy of the wave and the more energy it possesses.
