Physics for Computing Midterms Reviewer Flashcards

Flashcards reviewing heat and temperature, electrostatics, electric currents, vacuum tubes, semiconductors, transistors (BJTs and MOSFETs), and CMOS logic from the Physics for Computing lecture notes.

What are the two components that make up internal energy?

Internal energy consists of internal potential energy, which happens during molecular interaction, and internal kinetic energy, which happens during molecular motion (such as vibration, rotation, and translation).

How is temperature related to kinetic energy, and what three physical property changes can measure it?

Temperature is an indicator of an object's kinetic energy, where higher kinetic energy results in higher temperature. It can be measured based on changes in volume, pressure, or resistance.

What are the temperature conversion formulas between Celsius, Fahrenheit, and Kelvin?

The conversion formulas are: Celsius to Fahrenheit: ${^\circ\text{F}} = \frac{9}{5}{^\circ\text{C}} + 32$; Fahrenheit to Celsius: ${^\circ\text{C}} = \frac{5}{9}({^\circ\text{F}} - 32)$; Celsius to Kelvin: $K = {^\circ\text{C}} + 273.15$.

What are the boiling points and freezing points of water on the Celsius, Fahrenheit, and Kelvin scales?

Celsius: BP $100^\circ\text{C}$, FP $0^\circ\text{C}$; Fahrenheit: BP $212^\circ\text{F}$, FP $32^\circ\text{F}$; Kelvin: BP $373\,\text{K}$, FP $273\,\text{K}$.

What is the distinction between the notation ${^\circ\text{C}}$ and $\text{C}^\circ$?

The symbol ${^\circ\text{C}}$ denotes a specific temperature value in degrees Celsius, whereas $\text{C}^\circ$ denotes a temperature difference.

What is heat, and what are its three modes of transfer?

Heat is energy transferred from an object with high temperature to an object with low temperature. Its three modes of transfer are conduction (via contact), convection (via fluids), and radiation (via electromagnetic waves).

What is specific heat capacity, and what formula calculates thermal energy $Q$?

Specific heat capacity ($c$) is the energy required to change an object's temperature by $1$ degree. The thermal energy formula is $Q = m c \Delta T$, where $m$ is mass and $\Delta T$ is change in temperature.

What conditions must be satisfied for two objects to achieve thermal equilibrium?

Both objects must have the same temperature, and the net heat exchange between them must be equal to zero.

How does a bimetallic switch operate to open or close a circuit?

A bimetallic switch uses two bonded metals with different thermal expansion rates. Temperature changes force the strip to bend, which opens or closes electrical contacts in a circuit.

How does a vacuum flask prevent heat loss?

Heat transfer is blocked by a vacuum gap between double walls, silvered inner surfaces that reflect thermal radiation, and a stopper at the top that prevents heat from escaping.

What is the working principle of a heat sink?

A heat sink absorbs thermal energy via conduction from a device and radiates it into the surrounding air.

How does liquid cooling (coolant) manage thermal energy in computing systems?

Liquid cooling circulates fluid through an evaporator and condenser section to absorb heat from a source and radiate it away.

What distinguishes electrostatics from electric currents?

Electrostatics is the study of electric charges at rest (governed by Coulomb's Law), while electric currents is the study of charges in motion (governed by Ohm's Law).

What are the rules of electrostatic force, particle charges, and electrostatic equilibrium?

Like charges repel and unlike charges attract. Protons have a positive charge ($+$), electrons have a negative charge ($-$), and neutrons are neutral ($\pm$). Electrostatic equilibrium occurs when the net force is $0$.

What is Coulomb's Law formula and the value of Coulomb's constant $k$?

Coulomb's Law is $F = \frac{k q_1 q_2}{r^2}$, where $k = 9 \times 10^9\,\text{N\,m}^2/\text{C}^2$. Force $F$ is directly proportional to charges $q$ and inversely proportional to the square of the distance $r$ (halving distance quadruples force).

What working principle allows electric shielding to protect the inside of a conductor?

External electric fields cause charges to redistribute along the surface of a conductor, resulting in zero electric field inside ($\mathbf{E}_{\text{in}} = 0$).

How do E-inks use electrostatics to form visual images?

Charged particles (such as negatively charged black pigment and positively charged white pigment) move through clear fluid between top and bottom electrodes under an electric field to form visible images.

What is the working principle of a laser printer?

Charged toner transfers to laser-targeted areas on a photosensitive drum, and is then transferred onto electrostatic paper and fixed with rollers.

What formula calculates parallel-plate capacitance $C$, and what is the vacuum permittivity constant $\epsilon_0$?

The formula is $C = \frac{\epsilon_0 A}{d}$, where $\epsilon_0 = 8.85 \times 10^{-12}\,\text{F/m}$. Capacitance $C$ is directly proportional to plate area $A$ and inversely proportional to plate separation distance $d$.

How do capacitive keyboards and touch screens detect user input?

They sense changes in electrical capacitance caused by moving a plate or finger contact rather than relying on direct mechanical contact.

What is the difference in current flow paths between series and parallel circuits?

In a series circuit, current travels along only one path. In a parallel circuit, current flows through multiple distinct branches.

What is Ohm's Law and the functional roles of Voltage, Current, and Resistance?

Ohm's Law is $V = I R$. Voltage ($V$) acts as the energy source, Current ($I$) represents energy transport, and Resistance ($R$) acts as the energy converter.

What is the difference between conventional current direction and electron current direction?

Conventional current flows from positive to negative charge (high potential to low potential), whereas electron current flows from negative to positive charge.

What are the rules for Voltage, Current, and Resistance in a Series Circuit?

Voltage source splits across each resistor ($V_T = V_1 + V_2 + \dots$); Current flows through one path only ($I_T = I_1 = I_2 = \dots$); Resistance adds extra blockage ($R_T = R_1 + R_2 + \dots$).

What are the rules for Voltage, Current, and Resistance in a Parallel Circuit?

Voltage is equal across every branch ($V_T = V_1 = V_2 = \dots$); Current is split among branches ($I_T = I_1 + I_2 + \dots$); Resistance follows $\frac{1}{R_T} = \frac{1}{R_1} + \frac{1}{R_2} + \dots$, where adding branches makes current faster.

What is the working principle of an electrical fuse?

A fuse contains a conductive link designed to melt and break the circuit during current overloads.

How do mechanical relays compare to vacuum tubes in terms of speed and mechanical structure?

Mechanical relays are slow (millisecond response) and contain physical moving parts, whereas vacuum tubes are fast (microsecond response) and have no moving parts.

What is the process of thermionic emission?

Heat applied to a metal surface increases the kinetic energy of electrons; when heat exceeds the work function of the metal, electrons escape ('boiling off' electrons).

How does field emission release electrons from a metal surface?

A strong electrostatic field (voltage) applied between an anode and metal surface creates an intense positive charge on the anode that attracts electrons, bending the barrier so electrons quantum tunnel through.

What process triggers photoelectric electron emission?

High-frequency electromagnetic light photons collide with electrons, transferring energy; when photon energy exceeds the work function of the metal, electrons escape.

What process describes secondary electron emission (particle bombardment)?

High-speed primary particles (ions or electrons) collide with a metal surface, transferring kinetic energy to release new secondary electrons when their kinetic energy exceeds the work function.

What electron emission mode is utilized in vacuum tubes?

Vacuum tubes use thermionic emission.

What is the structural and operational difference between directly heated and indirectly heated vacuum tube diodes?

Directly heated diodes use the filament itself as the cathode (heats fast, but noise leaks into signal). Indirectly heated diodes use separate metal sleeves surrounding a heater wire to emit electrons, isolating heater noise.

What is the difference between external and internal suppressor grid connections in diodes?

An external connection connects to an outer pin to let designers adjust voltage, while an internal connection connects directly to the cathode inside to simplify design.

How does a vacuum tube diode operate to carry electric current?

Thermionic emission heats the cathode to release free electrons into the vacuum, which are then attracted to the positively charged anode.

What are the three voltage regions of a diode current-voltage curve?

Non-linear region ($0 - 7\,\text{V}$): Electrons form charge clouds as anode is too weak; Linear region ($7 - 25\,\text{V}$): Electrons are attracted with a proportional current increase; Saturation region ($> 25\,\text{V}$): No current increase as all thermally emitted electrons are attracted.

How does the control grid in a triode regulate electron flow between cathode and anode?

The control grid is placed between the cathode and anode. If the grid is positive ($+V$), electrons jump from cathode to anode; if the grid is negative ($-V$), electrons are repelled.

What physical characteristic defines semiconductors in terms of charge carriers?

In semiconductors, the number of free electrons is equal to the number of holes ($\text{no. of free electrons} = \text{no. of holes}$).

What are the four primary applications of semiconductors in computer hardware?

Logic (processes information as the brain in computing, e.g., microprocessors), Analog (converts analog signals to digital form), Memory (provides mass storage, e.g., flash drives), and Power (manages power using transistors/diodes).

How do the valence band and conduction band differ in semiconductors?

The valence band is the outermost electron shell involved in chemical bonding representing a stable low-energy state. The conduction band is a high energy band where free electrons enable electrical conduction.

How do band gap energies compare among conductors, semiconductors, and insulators?

Conductors have no band gap and overlapping conduction bands. Semiconductors have a moderate band gap ($1\,\text{eV}$) allowing jumps under conditions. Insulators have a large band gap ($5\,\text{eV}$) with minimal electron movement.

What is the difference between intrinsic and extrinsic semiconductors?

Intrinsic semiconductors are pure semiconductor materials. Extrinsic semiconductors are doped semiconductors where dopants are introduced to alter electrical properties.

How do pentavalent and trivalent dopants create N-type and P-type semiconductors?

Pentavalent dopants ($5$ valence electrons) create N-type semiconductors with extra electrons as negative charge carriers. Trivalent dopants ($3$ valence electrons) create P-type semiconductors with holes acting as positive carriers.

How do forward bias and reverse bias affect the depletion region of a PN junction?

Forward bias applies voltage that reduces the depletion region (ON state, electrons and holes move freely). Reverse bias applies voltage that increases the depletion region (OFF state, no charge carrier flow across junction).

What diode terminals connect to supply polarities in forward bias vs reverse bias?

In forward bias (ON state), N-type connects to negative ($-$) and P-type connects to positive ($+$). In reverse bias (OFF state), N-type connects to positive ($+$) and P-type connects to negative ($-$), forming a depletion region.

How does a Light Emitting Diode (LED) generate light energy?

An LED produces light when electric current pushes electrons from the conduction band to the valence band, releasing light energy.

How do terminal designations map between a Vacuum Tube, BJT, and FET?

Cathode maps to Emitter (BJT) and Source (FET); Grid maps to Base (BJT) and Gate (FET); Anode maps to Collector (BJT) and Drain (FET).

What is the dominant charge carrier and junction bias configuration in NPN vs PNP transistors?

NPN transistors have dominant electron charge carriers with a forward-biased base-emitter junction. PNP transistors have dominant hole charge carriers with a reverse-biased base-collector junction.

What terminal has the highest current in a BJT, and what is the current equation?

The emitter has the highest current, where $I_{\text{emitter}} = I_{\text{base}} + I_{\text{collector}}$.

What layers compose a Metal Oxide Substrate (MOS) structure?

A top Metal layer, a middle Oxide insulator layer, and a bottom Substrate (semiconductor) layer.

How do Enhancement and Depletion mode MOSFETs respond to gate voltage?

Enhancement mode is normally OFF at zero gate voltage (NMOS turns ON with positive gate; PMOS turns ON with negative gate). Depletion mode is normally ON without gate voltage (NMOS turns OFF with negative gate; PMOS turns OFF with positive gate).

How can PMOS and NMOS MOSFET schematic symbols be distinguished visually?

The PMOS symbol (a) features an inversion circle/bubble at the Gate terminal, while the NMOS symbol (b) has no bubble at the Gate terminal.

How are NMOS and PMOS transistors combined in CMOS logic for NAND and NOR gates?

In NAND logic, NMOS transistors are connected in series and PMOS transistors in parallel. In NOR logic, NMOS transistors are connected in parallel and PMOS transistors in series.

What are the states of NMOS and PMOS transistors in a CMOS inverter ($x = \bar{A}$) for inputs $A = 0$ and $A = 1$?

When input $A = 0$, NMOS is OFF, PMOS is ON, and output $x = 1$. When input $A = 1$, NMOS is ON, PMOS is OFF, and output $x = 0$.