38 Questions
What is the smallest part of an element or compound that normally exists in a free state?
Molecule
What is the ultimate particle to which an element can be reduced to?
Atom
How many elements occur naturally?
92
What is formed when 2 or more atoms of different elements combine?
Compound
What is made up of 2 hydrogen atoms and one oxygen atom?
Compound of water
What consists of one or more atoms of that element?
Molecule of an element
What can only combine to form compounds in certain fixed proportions?
Elements
What is the case with many substances met in everyday life?
They are mixtures of elements or compounds
What is an example of an application of electromagnetism principles?
Alternators
What is the prefix for 103?
kilo
What is the unit represented by the symbol 'μ'?
micro
What is the effect of increasing current flow on the magnetic field?
The magnetic field increases
What is the term for 10-6?
micro
What is the effect of high current flow on the filament of a light bulb?
It glows white hot
How would you express 35 milli-amperes in terms of amperes?
35 x 10^(-3) A
What is the term for 10^3?
kilo
What is the primary characteristic of a semiconductor?
It can switch between conducting and non-conducting states without damage.
What is the force used to switch semiconductors?
Voltage
What is the definition of static electricity?
Electricity that is standing still, or voltage potential with no electron flow
What is the relationship between the force between two point charges and the distance between them, according to Coulomb's Law?
The force between two point charges varies inversely with the distance between them.
What is the primary reason why atoms are said to attract each other?
Because they have unlike charges
What is the purpose of using silicon and germanium in semiconductor materials?
To allow the material to switch between conducting and non-conducting states
What is the primary mechanism behind a cell?
The use of two different metals placed in a liquid called an electrolyte
What is the term for the electrical charge acquired by an object, such as a comb, when it is rubbed against another object, such as hair?
Static electricity
What is the purpose of a thermocouple?
To measure the temperature difference between two junctions
What is the name of the effect that occurs when a quartz crystal is mechanically deformed, resulting in an electrical potential difference between its opposite faces?
Piezoelectric effect
What is the term for the devices that utilize the energy from a light source to produce electricity?
Photovoltaic cells
What is the primary cause of static electricity buildup on an aircraft in flight?
Friction between the aircraft's metal body and the atmosphere
What is the name of the scientist who discovered the thermoelectric effect?
Seebeck
What is the term for a group of cells that produce a battery?
Battery pack
How can the resistance of the lamp be obtained?
By dividing the voltmeter reading by the ammeter reading
What happens to the resistance of the filament as the temperature increases?
It increases
What is the temperature coefficient of resistance of pure metals like copper, iron, and tungsten?
Positive
What happens to the resistance of carbon, electrolytes, and insulating materials as the temperature increases?
It decreases
What is the characteristic of the resistance of certain alloys like manganin?
It remains constant with temperature
What is the resistance of the lamp at normal working temperature compared to when it is cold?
It is 10 times
What is the temperature at which the resistance of the copper wire was measured?
2000°C
What is the value of the resistance of the copper wire at 0°C?
1 ohm
Study Notes
Electron Theory
- Matter is composed of elements, which are the building blocks of all substances
- Elements can exist alone or combined to form compounds
- The smallest part of an element or compound that exists in a free state is called a molecule
- Molecules can consist of one or more atoms of the same element
- Compounds consist of two or more different elements
Structure of Matter
- Atoms are the ultimate particles of an element
- Many elements cannot exist in a stable form as individual atoms, but only in groups of atoms
- The properties of a substance depend on the arrangement of its atoms
Conduction
- Atoms attract each other, with like charges repelling and unlike charges attracting
- Static electricity is a force created by the attraction of unlike charges
- Coulomb's Law states that the force between two point charges varies inversely as the square of the distance between them and directly with the magnitude of charge
Chemical Action (Cell)
- A cell is formed by placing two different metals in a liquid called an electrolyte
- Grouping these cells together produces a battery
Fricton (Static Electricity)
- Static electricity is demonstrated by rubbing a silk cloth over a glass rod, which creates a stationary or "at rest" charge
- Aircraft in flight build up large amounts of static electricity due to friction, which can be undesirable but unavoidable
Pressure (Crystal Controlled Oscillators)
- Certain crystalline substances, like quartz, exhibit a piezoelectric effect, resulting in a potential difference between opposite faces of the crystal when mechanically deformed
- The crystal can be shown to have an 'electrical' equivalent circuit
Light (Photovoltaic Cells)
- Photovoltaic cells use energy from a light source to produce electricity
- These devices can be used to power battery chargers when connected as solar panels
Heat (Thermocouple)
- When two different metals are placed in contact, an electrical potential difference exists, depending on the temperature of the junction
- This thermoelectric effect is called the Seebeck effect, and the junction is called a 'thermocouple'
Electromagnetism
- When current flows, a small magnetic field is created, and the higher the current flow, the stronger the magnetic field
- Electromagnetic principles are used in alternators, ignition systems, and other electronic devices
This quiz is about measuring the resistance of a lamp by varying the filament temperature and voltage. It covers the relationship between voltage, current, and resistance.
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