Sri Lanka Scientific Service Exam flashcards

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

SI unit of force

The newton (N) is the SI unit of force; one newton is the force that accelerates a one-kilogram mass at one metre per second squared (1 N = 1 kg·m/s²).

Newton's second law

The net force on an object equals its mass times its acceleration (F = ma); force and acceleration are vectors in the same direction.

Ohm's law

For an ohmic conductor at constant temperature, current is directly proportional to voltage: V = IR, where R is resistance in ohms.

Ideal gas law

PV = nRT relates pressure, volume, amount in moles, and absolute temperature; R is the universal gas constant, approximately 8.314 J/(mol·K).

pH definition

pH = −log₁₀[H⁺], where [H⁺] is hydrogen ion concentration in moles per litre; pH below 7 is acidic, above 7 is basic at 25 °C.

Percent error formula

Percent error = (|experimental value − accepted value| / accepted value) × 100%; it quantifies the accuracy of a measurement against a reference value.

Dimensional analysis

A method that checks equations by confirming both sides have the same base dimensions (mass, length, time, etc.) and converts units using conversion factors.

Cell theory

All living organisms are made of one or more cells, the cell is the basic unit of life, and all cells arise from pre-existing cells by division.

DNA base pairing

In DNA, adenine pairs with thymine via two hydrogen bonds, and guanine pairs with cytosine via three hydrogen bonds, keeping the double helix uniform.

Michaelis–Menten equation

v = Vmax[S]/(Km + [S]) describes enzyme kinetics; Km is the substrate concentration at which the reaction velocity is half of Vmax.

Hardy–Weinberg equilibrium

In a large, randomly mating population without selection, mutation, or migration, allele frequencies remain constant: p² + 2pq + q² = 1.

First law of thermodynamics

Energy cannot be created or destroyed; the change in internal energy equals heat added to the system minus work done by the system (ΔU = Q − W).

First-order reaction half-life

For a first-order reaction, half-life is independent of initial concentration and equals ln2/k, approximately 0.693/k, where k is the rate constant.

Central dogma

Genetic information flows from DNA to RNA to protein: replication copies DNA, transcription makes RNA, and translation synthesises protein on ribosomes.

Periodic table trends

Atomic radius decreases across a period and increases down a group; electronegativity increases across a period and decreases down a group.

Null hypothesis

The null hypothesis (H₀) proposes no effect, no difference, or no association between variables; statistical tests assess whether data are compatible with it.

Type I error

A Type I error is rejecting a true null hypothesis (false positive); its probability is the significance level α, commonly set at 0.05.

Type II error

A Type II error is failing to reject a false null hypothesis (false negative); its probability is β, and statistical power equals 1 − β.

p-value

The probability of obtaining a result at least as extreme as the observed data, assuming the null hypothesis is true; H₀ is rejected when p < α.

Standard error of mean

SEM = s/√n, where s is the sample standard deviation and n is sample size; it estimates the variability of sample means around the population mean.

Pearson correlation coefficient

r ranges from −1 to +1 and measures the strength and direction of a linear association between two continuous variables; it does not imply causation.

Randomisation

Random assignment of participants or samples to groups distributes known and unknown confounders evenly, reducing selection bias in comparative studies.

Sensitivity and specificity

Sensitivity is the proportion of true positives correctly identified; specificity is the proportion of true negatives correctly identified by a test.

Parametric versus non-parametric

Parametric tests assume normal distribution and equal variances; non-parametric tests such as Mann–Whitney U make fewer distributional assumptions.

Informed consent

Voluntary agreement by a competent participant after disclosure of the study's purpose, procedures, risks, benefits, alternatives, and right to withdraw.

Research ethics committee

An independent board that reviews research protocols involving humans or animals to ensure ethical standards and participant welfare before the study begins.

Authorship criteria

Authorship requires substantial contribution to conception, design, data collection, or analysis, plus drafting or critical revision and approval of the final version.

Plagiarism

Presenting another person's ideas, words, data, or images as one's own without proper attribution or citation, violating research integrity.

Conflict of interest

A situation where financial or personal interests could bias professional judgement; it must be disclosed in publications, grants, and peer review.

Data fabrication

Inventing or altering data or results and recording them as if they were genuine observations; a serious form of research misconduct.

Good laboratory practice

A quality system covering organisation, standard operating procedures, equipment calibration, and traceable raw data to ensure reliability of non-clinical studies.

Peer review confidentiality

Reviewers must keep manuscripts and data confidential, avoid using unpublished content, and decline review when a conflict of interest exists.