Atomic Theory Flashcards
Definition of matter
Anything that has mass and occupies space
Three states of Matter
Solid, Liquid, Gas
What is the most basic component of all matter?
The atom
What does an atom consist out of?
Protons, Neutrons, and electrons.
What does the nucleus of an atom consist of?
Protons and neutrons bound together by extremely powerful strong nuclear forces
In it’s normal state, how many electrons orbits the nucleus of an atom?
A number of electrons equal to the number of protons in the nucleus
What is the charge of an atom in it’s normal state?
Zero, because the number of electrons and protons are equal, which cancels out any charge.
What are the orbits in which electrons rotate around the nucleus called?
Shells
When does an atom become “Ionized”?
When it loses or gains one or more electrons and as a result has either a net positive or net negative charge.
What is the charge of an electron?
Negative
What is the charge of a proton?
Positive
What is the law of electrical charges?
like charges repel, and unlike charges attract
What keeps the electrons in orbit?
The equal and opposite charges between the protons and electrons.
What accounts for the electrons being spaced equidistant from each other?
The like charges between the electrons repel each other, resulting in an equidistant spacing from one another
What is an electron?
A negatively charged particle of an atom.
What is conventional flow?
The idea that “charge” flows from positive to negative
What is the unit of conventional and electron current flow?
The Ampere
Where is conventional flow most often used?
Heavy current, or Electrical Trade Theory
What is electron flow?
The idea that electrons flow from negative to positive.
4 basic components of a circuit
- Power Supply
- A load (a light, resistor, a motor)
- Conductor (like copper wire)
- A Switch
Definition of current
The flow of electricity through a conductor.
OR
The flow of electrons in a particular direction through a material.
OR
The flow or movement of “charge” from one atom to the next
What direction does current flow?
Current always flows from positive to negative
How does current flow in a conductor?
In some elements the orbiting electrons in the outer shell (valence shell) are loosely bonded. the attraction that the positive nucleus has on those electrons is relatively small and are known as free electrons.
These free electrons experience an attraction towards neighboring atoms and quite easily move int orbit around them.
When this happens the atom from which the electron came is left with a net positive charge (positive ion) which causes it to attract electrons from other atoms.
So if a cell is connected across the ends of the conductor a potential difference will exist, in other words one end will be positive and the other negative. The free electrons will be attracted towards the positive end and they will drift in that direction.
When is a material a good conductor?
When it is made of an element with free electrons.
Definition of a conductor
A substance through which an electrical current can flow easily.
What is a Coulomb (C)
The unit in which “charge” is measured. 1 Coulomb has a total charge of 6.2 x 10^18 electrons.
1 Coulomb = 1 Ampere x 1 second or 1A/s
What is Ampere?
It is the measure of how fast the charge or current is moving past a specific point in an electrical circuit.
What is the elementary charge
The charge of a single electron.
-1.602176634 x 10^-19 C
What is the formula for charge?
Q = N x e
Q = Charge in Coulomb
N = number of electrons
e = elementary charge (1.6 x 10^-19)
What does it mean when the current in a circuit is 1 Ampere?
1 Coulomb of charge passes a point in the circuit every second.
1 A = 1C/s
How many electrons in one Coulomb?
6.2 x 10^18 electrons for every negative Coulomb
Law of conservation of electric charge
It says that you can never create a net electric charge. Instead, charge can only move from one place to another.
How to calculate the force between particles?
F = k / ((q1*q2) / r2)
F = force in newtons
k = Coulomb’s constant
q1 = the charge of the first particle
q2 = the charge of the second particle
r2 = distance between particles squared
If the answer is positive, then the particles repel one another.
Difference between AC and DC current.
DC - direct current
Flows only in one direction from negative to positive. Products in a dc circuit needs to be connected the correct way in terms of their polarity
AC - alternating current
The current in an AC circuit surges forwards and backwards approx 50 times a second (50 Hz in household AC)
What is potential difference?
The difference in energy between two points in a circuit is called the potential difference. It is the electrical pressure that causes current to flow. Potential difference is measured in Volts.
In relation to EMF, it is the energy dissipated by a unit of charge.
What is a Volt?
The energy transferred (joules) per unit of charge (Coulomb) to move a positive charge from one point to another.
OR
The energy in Joules carried by one Coulomb of charge
OR
The difference in electrical energy per coulomb between two points in an electrical circuit.
1 V = 1 Joule per coulomb or V = E/Q
What are sources of potential difference?
Chemical Sources: Cells, Batteries
Mechanical Sources: Alternators,
Dynamos: Generators (turns diesel into electricity)
What is EMF?
Electromotive force:
A current is a flow of charges. EMF is the force that causes the charges to flow. It is the energy supplied to a unit of charge by a source.
It is measured in Volts. 1 Volt is 1 Joule/Coulomb
What is the difference between EMF and Potential Difference
Both are measured in Volts
EMF is the work done (J) to drive per unit charge (C) across a circuit. E = W/Q
PD is the work done (J) to drive per unit charge (C) across 2 points in a circuit E = W/Q
Electrical Resistance
The opposition offered to the flow of current
4 Factors that influence resistance
- Length
- Thickness
- Material Type
- Heat
Insulator
An element or substance that prevents the flow of current, due to having no free electrons
Properties of Good Insulators
- High resistance to the flow of electricity
- Able to withstand mechanical stress (Durable)
- Able to withstand high temperatures
- Non-Absorbent
- Able to withstand chemical erosion
Explain the concept of “charge”
charge or “Electric charge” is a property of certain subatomic particles that causes them to experience a force when placed in an electromagnetic field.
There are 3 types of charges
Positive Charge: Carried by protons.
Negative Charge: Carried by electrons.
Neutral Charge: Neutrons have no charge
Charge can be quantified, and is measured in Coulombs, which is denoted as Q or C
