About this quiz
Basic physics and chemistry facts including SI units, light, heat, acids and bases, chemical symbols, gases, lenses and electricity.
This Lok Sewa practice set has 20 multiple-choice questions (Subject: General Knowledge · For: Kharidar, Nayab Subba · Level: Easy). Take the quiz above first; after that, use the study list below to revise every question with its correct answer and a short explanation.
Study list: all 20 questions with answers and explanations
What is the SI unit of force?
- A) Joule
- B) Watt
- C) Newton ✔
- D) Pascal
Why: Force is measured in newtons (N), named after Sir Isaac Newton.
What is the SI unit of electric current?
- A) Ampere ✔
- B) Volt
- C) Ohm
- D) Coulomb
Why: Electric current is measured in amperes (A), one of the seven SI base units.
What is the SI unit of power?
- A) Joule
- B) Newton
- C) Ampere
- D) Watt ✔
Why: Power, the rate of doing work, is measured in watts (W); one watt equals one joule per second.
What is the SI unit of frequency?
- A) Decibel
- B) Hertz ✔
- C) Tesla
- D) Kelvin
Why: Frequency is measured in hertz (Hz), meaning cycles per second.
Approximately what is the speed of light in a vacuum?
- A) 3 x 10^5 metres per second
- B) 3 x 10^6 metres per second
- C) 3 x 10^10 metres per second
- D) 3 x 10^8 metres per second ✔
Why: Light travels at about 3 x 10^8 metres per second (about 300,000 km per second) in a vacuum.
At standard atmospheric pressure, at what temperature does pure water boil?
- A) 100 degrees Celsius ✔
- B) 90 degrees Celsius
- C) 110 degrees Celsius
- D) 212 degrees Celsius
Why: Pure water boils at 100 degrees Celsius (212 degrees Fahrenheit) at standard sea-level pressure.
At what temperature does pure water freeze on the Celsius scale?
- A) 4 degrees Celsius
- B) minus 10 degrees Celsius
- C) 0 degrees Celsius ✔
- D) 32 degrees Celsius
Why: Pure water freezes at 0 degrees Celsius, which equals 32 degrees Fahrenheit.
Absolute zero (0 Kelvin) is approximately equal to which Celsius temperature?
- A) minus 100 degrees Celsius
- B) minus 373 degrees Celsius
- C) 0 degrees Celsius
- D) minus 273 degrees Celsius ✔
Why: Absolute zero is 0 K, which is minus 273.15 degrees Celsius.
What is the pH of pure water at 25 degrees Celsius?
- A) 0
- B) 7 ✔
- C) 1
- D) 14
Why: Pure water is neutral with a pH of 7; values below 7 are acidic and above 7 are basic.
What colour does an acid turn blue litmus paper?
- A) Red ✔
- B) Green
- C) Yellow
- D) Remains blue
Why: Acids turn blue litmus red, while bases turn red litmus blue.
Which acid is present in vinegar?
- A) Citric acid
- B) Lactic acid
- C) Acetic acid ✔
- D) Hydrochloric acid
Why: Vinegar is a dilute solution of acetic acid (ethanoic acid).
What is the chemical symbol of sodium?
- A) So
- B) S
- C) Sd
- D) Na ✔
Why: The symbol Na comes from the Latin name for sodium, natrium.
What is the chemical symbol of iron?
- A) Ir
- B) Fe ✔
- C) In
- D) I
Why: The symbol Fe comes from the Latin word ferrum, meaning iron.
What is the chemical formula of common salt?
- A) KCl
- B) NaOH
- C) CaCO3
- D) NaCl ✔
Why: Common salt is sodium chloride, with the formula NaCl.
Which is the most abundant gas in the Earth's atmosphere?
- A) Oxygen
- B) Carbon dioxide
- C) Nitrogen ✔
- D) Argon
Why: Nitrogen makes up about 78 percent of the Earth's atmosphere, and oxygen about 21 percent.
Which gas is commonly known as laughing gas?
- A) Nitrous oxide ✔
- B) Nitrogen dioxide
- C) Carbon monoxide
- D) Sulphur dioxide
Why: Nitrous oxide (N2O) is called laughing gas and is used as a mild anaesthetic.
Which type of lens is used to correct short-sightedness (myopia)?
- A) Convex lens
- B) Concave lens ✔
- C) Cylindrical lens
- D) Prism
Why: A concave (diverging) lens corrects myopia by spreading light rays so the image forms on the retina.
Which type of lens is used as a simple magnifying glass?
- A) Convex lens ✔
- B) Concave lens
- C) Plane glass
- D) Plano-concave lens
Why: A convex (converging) lens produces an enlarged image of a nearby object, so it is used as a magnifying glass.
In what unit is electrical resistance measured?
- A) Volt
- B) Ampere
- C) Ohm ✔
- D) Watt
Why: Resistance is measured in ohms; by Ohm's law, voltage equals current multiplied by resistance (V = IR).
Which instrument is used to measure electric current in a circuit?
- A) Voltmeter
- B) Ammeter ✔
- C) Thermometer
- D) Barometer
Why: An ammeter is connected in series in a circuit to measure electric current.