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Questions and Answers
What is the charge of protons in an atom?
What is the charge of protons in an atom?
Which type of electron has the capability to move freely and contribute to electrical conductivity in metals?
Which type of electron has the capability to move freely and contribute to electrical conductivity in metals?
What characteristic do good conductors like copper and aluminum share regarding their valence electrons?
What characteristic do good conductors like copper and aluminum share regarding their valence electrons?
How many valence electrons does germanium possess to classify as a semiconductor?
How many valence electrons does germanium possess to classify as a semiconductor?
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What type of material has more than four valence electrons and is also considered an insulator?
What type of material has more than four valence electrons and is also considered an insulator?
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What describes the arrangement of atoms in solid conductors like copper and aluminum?
What describes the arrangement of atoms in solid conductors like copper and aluminum?
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What is the primary reason for the conduction process in metals?
What is the primary reason for the conduction process in metals?
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In the atomic theory, what does an atomic orbital represent?
In the atomic theory, what does an atomic orbital represent?
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What is the concentration of free electrons in aluminum per cubic inch?
What is the concentration of free electrons in aluminum per cubic inch?
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What is the charge of one negatively charged electron in coulombs?
What is the charge of one negatively charged electron in coulombs?
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If a current of 3 amperes flows for 8 seconds, what is the total charge transferred in coulombs?
If a current of 3 amperes flows for 8 seconds, what is the total charge transferred in coulombs?
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How much current in amperes will be produced if 200 Coulombs pass through a conductor in 1.2 minutes?
How much current in amperes will be produced if 200 Coulombs pass through a conductor in 1.2 minutes?
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What is the total charge in coulombs if the current changes from 0 to 3 A uniformly over 3 seconds?
What is the total charge in coulombs if the current changes from 0 to 3 A uniformly over 3 seconds?
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How many free electrons are in a copper conductor with a length of 1000 feet?
How many free electrons are in a copper conductor with a length of 1000 feet?
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What is the meaning of one ampere in terms of coulombs and time?
What is the meaning of one ampere in terms of coulombs and time?
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If the current in a conductor drops from 3 A to 1.5 A over 7 seconds, what does this imply about the flow of charge?
If the current in a conductor drops from 3 A to 1.5 A over 7 seconds, what does this imply about the flow of charge?
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Which of the following defines resistivity in a material?
Which of the following defines resistivity in a material?
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What is one characteristic of unidirectional direct current?
What is one characteristic of unidirectional direct current?
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Which material has the highest resistivity at 20 °C?
Which material has the highest resistivity at 20 °C?
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How does resistance change according to the length of a conductor when volume is fixed?
How does resistance change according to the length of a conductor when volume is fixed?
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Which type of current exhibits a steady flow of electric charge in one direction?
Which type of current exhibits a steady flow of electric charge in one direction?
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What is the relationship between resistance and the cross-section of a conductor when the volume is fixed?
What is the relationship between resistance and the cross-section of a conductor when the volume is fixed?
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Which of the following is true about alternating current?
Which of the following is true about alternating current?
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What is the resistivity of annealed copper at 20 °C?
What is the resistivity of annealed copper at 20 °C?
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Study Notes
Atomic Structure
- All matter, whether gaseous, liquid, or solid, is composed of atoms.
- Atoms are made of fundamental subatomic particles: protons, neutrons, and electrons.
- Protons are positively charged particles located inside the atom's nucleus.
- Electrons have a negative charge and are found surrounding the nucleus.
- Neutrons are neutral subatomic particles found in the nucleus.
Orbital Electrons
- Negatively charged electrons revolve around the positively charged nucleus in specific orbits.
- These orbits are related to energy levels.
- An atomic orbital describes both the location and wave-like behavior of an electron within an atom.
- An electron in an atom possesses three types of energy.
- The energy required to move the electron from the nucleus.
- The energy of electron's motion around the nucleus.
- The energy from its spin on its own axis.
Valence Electrons and Conductivity in Solids
- Atoms combine in regular patterns to form solids, which can be electrical conductors.
- Silver, copper, and aluminum are common conductors with a cubic crystal structure.
- The crystal lattice structure is maintained by valence electrons (electrons in the outermost shell).
- These valence electrons are free to move between atoms in conductors, enabling the conduction process.
Electrical Conductivity
- Solid materials can be classified as conductors, insulators, or semiconductors based on their electrical conductivity.
- Good conductors have fewer than four valence electrons (e.g., copper, aluminum).
- Poor conductors (insulators) have more than four valence electrons (e.g., phosphorus).
- Semiconductors have exactly four valence electrons (e.g., germanium).
- Copper, silver, and aluminum are excellent conductors due to a large number of free electrons.
Electric Charge and Electric Current
- Electric current involves the transfer of electric charge.
- Applying an electric pressure to a conductor moves free electrons, creating a current.
- The unit of charge is the coulomb (C).
- One coulomb corresponds to 6.28 x 10^18 electrons.
- One ampere (A) of current is one coulomb of charge passing a point per second.
- Current is calculated as charge (Q) divided by time (t): I = Q/t
Quiz No. 1
- Calculate the total charge transferred in a conductor with fluctuating current over a 15-second period. The current changes uniformly from 0 to 3 amperes in 3 seconds, remains steady at 3 amperes for 5 seconds, and then drops uniformly to 1.5 amperes in 7 seconds.
Sample Problem (Copper)
- Calculate the number of free electrons in a copper conductor with a diameter of 0.064 inches and a length of 1000 feet.
Sample Problem
- Calculate the current in amperes if 1000 Coulombs pass through a conductor in 2 minutes.
Quiz No. 2
- Determine if a fuse rated at 4 amperes will blow if 200 Coulombs pass through it in 1.2 minutes.
Electron Velocity in Conductors (Copper)
- Calculate electron velocity given current and cross-sectional area of a copper conductor.
Electron Velocity in Conductors (Aluminum and Silver)
- Calculate electron velocity for aluminum and silver conductors, using their respective free electron densities.
Sample Problem (Copper and Aluminum)
- Given a current and cross-sectional area, calculate the electron velocity for both copper and aluminum conductors.
Quiz no. 3
- Determine the number of trips of load current on a copper wire in 24 hours, given current, wire cross-sectional area and length
EMF (Electromotive Force) or Voltage
- EMF is the characteristic of a device that creates electron flow.
- Examples are batteries and generators.
Electrical Resistance and Resistivity
- Resistivity is a material property representing its resistance to current flow.
- Resistance of a conductor is directly proportional to its length and inversely proportional to the conductor's cross-sectional area.
- Important materials and their resistivity values are listed.
Volume Resistivity
- Resistance of a conductor varies directly with the square of its length if the conductor volume remains constant.
Sample Problem (Resistance of a copper wire)
- Calculate the resistance of a 3500-foot copper wire with a 0.5-inch diameter and a resistivity of 1.724μΩ-cm.
Sample Problem (Resistance of a bus bar)
- Calculate the resistance of a 10 meter long copper bus bar with a 4x4 cm² cross-section.
Kinds of Current
- Unidirectional Direct Current: Current that varies in magnitude but does not reverse direction.
- Direct Current (DC): A steady flow of electric charge in one direction.
- Pulsating Direct Current: Current with varying magnitude but steady direction.
- Alternating Current (AC): Current that changes regularly in both magnitude and direction.
- Oscillating Current: A current that alternates in magnitude and direction.
Kinds of Voltage
- Voltages (EMF), like currents, can be DC or AC (alternating) and vary in magnitude and/or direction. A/C voltages are also known as oscillating voltages.
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Description
Test your knowledge on atomic structure, orbital electrons, and the significance of valence electrons in conductivity. This quiz covers fundamental concepts of how atoms are composed and how electrons behave within them. Ideal for students studying chemistry or physics.
