PPSC Past Papers 2026 Solved

Correct answer: Gabriel Fahrenheit. Daniel Gabriel Fahrenheit invented the mercury thermometer in 1714.

Background: Fahrenheit made the first practical mercury thermometer in 1714 and later introduced the Fahrenheit scale.

• Einstein: Einstein is known for relativity.
• Thomas Albert: Thomas Albert is not credited with this invention.
• Galileo: Galileo invented an early thermoscope, not the mercury thermometer.

Did you know? On his scale water freezes at 32°F and boils at 212°F.

Memory trick: F for Fahrenheit, F for Freezing at 32°F.

Correct answer: 360°. A geostationary satellite completes a full 360° rotation in 24 hours, the same as the Earth, so it stays above one point.

Background: A geostationary satellite orbits about 35,786 km above the equator and takes 24 hours for one orbit, the same time the Earth takes to rotate once (360°).

• 120°: 120° is only a third of a full rotation.
• 180°: 180° is only half a rotation.
• 270°: 270° is only three-quarters of a rotation.

Did you know? Pakistan’s communications satellite PakSat-1R is in geostationary orbit.

Memory trick: Geostationary = stays still above one spot → one 360° turn per 24 hours.

Correct answer: 20–20,000 Hz. Humans can normally hear sounds from about 20 Hz to 20,000 Hz.

Background: Sound frequency is measured in hertz (Hz). Young humans can normally hear from about 20 Hz to 20,000 Hz.

• 20–200 Hz: 20–200 Hz covers only very low sounds.
• 20–2000 Hz: 20–2000 Hz excludes higher sounds humans can hear.
• None of these: “None of these” is incorrect because 20–20,000 Hz is correct.

Did you know? Sound below 20 Hz is infrasound and above 20,000 Hz is ultrasound, which bats use to navigate.

Memory trick: 20 to 20,000 (20 Hz → 20 kHz).

Correct answer: 1. Hydrogen has one proton, so its atomic number is 1.

Background: The atomic number is the number of protons in an atom’s nucleus. Hydrogen has one proton.

• 0: 0 would mean no protons.
• −1: Atomic numbers cannot be negative.
• 2: 2 is the atomic number of helium.

Did you know? Hydrogen is the lightest and most abundant element in the universe. Its name means “water-former”.

Memory trick: H = element number 1.

Correct answer: International System of Units. SI stands for Système International d’Unités, the International System of Units.

Background: SI stands for Système International d’Unités. It was adopted in 1960 and is the metric system used worldwide in science.

• System Instrument: “System Instrument” is not correct.
• System Enterprise: “System Enterprise” is not correct.
• Internal System: “Internal System” is not correct.

Did you know? It has seven base units: metre, kilogram, second, ampere, kelvin, mole, and candela. In 2019 the units were redefined using fundamental constants of nature.

Memory trick: Seven base units: M-K-S-A-K-M-C (“My Kind Sister Always Keeps Making Candy”).

Correct answer: Atmospheric pressure. Atmospheric pressure is the force that the weight of the air exerts on the Earth’s surface.

Background: Air has weight, so the air column above any surface presses down on it. At sea level this pressure is about 101,325 pascals (1 atmosphere).

• Wind: Wind is the horizontal movement of air.
• Low pressure: Low pressure is a condition of weaker pressure, not the force itself.
• None of these: “None of these” is incorrect because atmospheric pressure is correct.

Did you know? Evangelista Torricelli invented the mercury barometer in 1643 to measure it.

Memory trick: Weight of air → pressure; the barometer measures it.

Correct answer: Wilhelm Röntgen. Wilhelm Conrad Röntgen discovered X-rays in 1895.

Background: Wilhelm Conrad Röntgen discovered X-rays on 8 November 1895 in Würzburg, Germany.

• Edison: Edison is known for the phonograph and the practical light bulb.
• Marie Curie: Marie Curie is known for radioactivity (polonium and radium).
• Robert Bunsen: Robert Bunsen is known for the Bunsen burner.

Did you know? He called them “X” rays because their nature was unknown, and won the first Nobel Prize in Physics in 1901.

Memory trick: X = unknown → Röntgen.

Correct answer: Radar. Robert Watson-Watt developed radar in the 1930s.

Background: RADAR stands for Radio Detection And Ranging. Robert Watson-Watt developed it in Britain in the 1930s to detect aircraft.

• Needle: He did not invent the needle.
• Tube light: He did not invent the tube light.
• None of these: “None of these” is incorrect because radar is correct.

Did you know? Radar helped Britain in the Battle of Britain in 1940.

Memory trick: Watson-Watt → RADAR.