BCS Written General Science & Tech flashcards

32 cards. Read the term and the definition here. The deck at the top of this page is optional.

Newton's Second Law

Net force on a body equals mass times acceleration (F = ma). Acceleration is in the direction of the net force and inversely proportional to mass.

Ohm's Law

Current through a conductor is proportional to voltage across it and inversely proportional to resistance: V = IR, valid for ohmic materials at constant temperature.

pH Scale

pH equals the negative base-10 logarithm of hydrogen ion concentration. Values below 7 are acidic, 7 neutral, and above 7 basic at 25 degrees Celsius.

Mole

Amount of substance containing 6.022 × 10²³ elementary entities. Its mass in grams equals the relative molecular mass of the substance.

Isotopes

Atoms of the same element with equal proton numbers but different neutron numbers. They share chemical behaviour but differ in mass and nuclear stability.

Prokaryote vs Eukaryote

Prokaryotes lack a membrane-bound nucleus and organelles; eukaryotes have a nucleus, mitochondria, and other membrane-bound compartments, and are generally larger.

Photosynthesis Equation

Six carbon dioxide molecules plus six water molecules, using light energy, yield one glucose molecule and six oxygen molecules inside chloroplasts.

Base Pairing Rule

In DNA, adenine pairs with thymine and guanine with cytosine; in RNA, adenine pairs with uracil. Guanine-cytosine pairs form three hydrogen bonds.

Enzyme Function

Enzymes are protein catalysts that lower a reaction's activation energy without being consumed. Activity depends on temperature, pH, and substrate concentration.

Monohybrid Cross Ratio

Crossing two heterozygotes for one gene gives a 3:1 phenotypic ratio and a 1:2:1 genotypic ratio when dominance is complete.

Incidence vs Prevalence

Incidence counts new cases arising in a population at risk over a period; prevalence counts all existing cases at a given time.

Herd Immunity Threshold

Approximately 1 minus 1/R₀. It is the fraction of a population needing immunity before an infectious disease stops spreading.

Sensitivity and Specificity

Sensitivity is the proportion of diseased people correctly identified as positive; specificity is the proportion of healthy people correctly identified as negative.

Case Fatality Rate

Deaths from a disease divided by diagnosed cases of that disease, multiplied by 100. It measures severity among detected cases, not overall mortality.

Levels of Prevention

Primary prevents disease onset through exposure control; secondary detects disease early by screening; tertiary reduces disability and complications after disease is established.

Binary to Decimal

Each binary digit represents a power of two by position from the right, starting at 2⁰. Sum the values where the digit is 1.

Volatile vs Non-Volatile Memory

Volatile memory such as RAM loses contents when power is removed; non-volatile memory such as ROM or flash retains data without power.

TCP vs UDP

TCP provides ordered, reliable delivery with acknowledgements and retransmission; UDP sends datagrams without guarantees, suiting low-latency real-time traffic.

Symmetric vs Asymmetric Encryption

Symmetric encryption uses one shared secret key for both directions; asymmetric encryption uses a public key to encrypt and a matched private key to decrypt.

Primary Key

A column or set of columns uniquely identifying each row in a relational table. It cannot contain duplicate or null values.

Stress and Strain

Stress is force per unit cross-sectional area; strain is the fractional change in length. Their ratio in the elastic region is Young's modulus.

First Law of Thermodynamics

Change in internal energy equals heat added to the system minus work done by the system. Energy is conserved in every process.

Carnot Efficiency

Maximum efficiency of a heat engine is 1 minus the cold reservoir temperature divided by the hot reservoir temperature, both in kelvin.

Mechanical Advantage

For a lever, load divided by effort, equal to effort arm divided by load arm. Values above one mean the load exceeds the applied effort.

Overfitting

A model fits training data including its noise, so accuracy on training is high while accuracy on unseen test data is poor.

CRISPR-Cas9

A gene-editing system in which a guide RNA directs the Cas9 nuclease to a matching DNA sequence, where it creates a double-strand break.

Capacity Factor

Actual energy generated over a period divided by the maximum possible output at rated power over that period, usually expressed as a percentage.

Falsifiability

A scientific hypothesis must make predictions that could be shown false by observation. Claims immune to any possible contrary evidence are not empirically testable.

Control Group

Participants or samples receiving no active treatment, or a placebo, providing a baseline against which the intervention's effect is measured.

p-value Meaning

The probability of obtaining data at least as extreme as observed, assuming the null hypothesis is true. It is not the probability that the null is true.

Greenhouse Effect

Atmospheric gases absorb outgoing infrared radiation and re-emit it, warming the surface. Concentration and potency determine each gas's contribution.

Eutrophication

Nutrient enrichment of water, mainly by nitrogen and phosphorus, causing algal blooms whose decay depletes dissolved oxygen and harms aquatic life.