Here are 25 multiple-choice questions on Basic Science (Physics) tailored for the JKSSB Forester exam, covering fundamental concepts from 12th standard physics, along with answers and explanations:
Basic Science (Physics) – Multiple Choice Questions
Q1. Which of the following is NOT a fundamental quantity in the International System of Units (SI)?
(a) Length
(b) Mass
(c) Force
(d) Time
Answer: (c)
Explanation: Fundamental quantities are independent of each other. Length, mass, and time are fundamental. Force is a derived quantity (Force = mass × acceleration).
Q2. The unit of electric current in SI is:
(a) Volt
(b) Ampere
(c) Ohm
(d) Watt
Answer: (b)
Explanation: Electric current is measured in Ampere (A). Volt is for potential difference, Ohm for resistance, and Watt for power.
Q3. What is the SI unit of power?
(a) Joule
(b) Newton
(c) Watt
(d) Pascal
Answer: (c)
Explanation: Power is the rate at which work is done or energy is transferred, and its SI unit is the Watt (W). Joule is for energy/work, Newton for force, and Pascal for pressure.
Q4. The phenomenon responsible for the bending of light when it passes from one medium to another (e.g., air to water) is called:
(a) Reflection
(b) Refraction
(c) Diffraction
(d) Dispersion
Answer: (b)
Explanation: Refraction is the bending of light as it passes from one transparent medium to another due to a change in its speed.
Q5. Concave mirrors are used in:
(a) Rear-view mirrors in vehicles
(b) Shaving mirrors
(c) Street lights
(d) Periscopes
Answer: (b)
Explanation: Concave mirrors produce magnified, upright images when an object is placed between the pole and the principal focus, making them suitable for shaving mirrors and dentists’ mirrors. Rear-view mirrors use convex mirrors, and periscopes use plane mirrors.
Q6. Which of the following colors of light has the shortest wavelength?
(a) Red
(b) Green
(c) Blue
(d) Violet
Answer: (d)
Explanation: In the visible spectrum (VIBGYOR), violet light has the shortest wavelength and highest frequency, while red light has the longest wavelength and lowest frequency.
Q7. Ohm’s Law states the relationship between:
(a) Voltage and Current
(b) Current and Resistance
(c) Voltage, Current, and Resistance
(d) Power and Resistance
Answer: (c)
Explanation: Ohm’s Law states that for a metallic conductor at constant temperature, the current flowing through it is directly proportional to the potential difference across its ends (V = IR), thus relating Voltage, Current, and Resistance.
Q8. The material that allows electric current to pass through it easily is called a:
(a) Insulator
(b) Conductor
(c) Semiconductor
(d) Dielectric
Answer: (b)
Explanation: Conductors are materials that have free electrons, allowing electric current to flow easily through them. Examples include metals.
Q9. What is the phenomenon of splitting of white light into its constituent colors called?
(a) Reflection
(b) Refraction
(c) Dispersion
(d) Scattering
Answer: (c)
Explanation: Dispersion is the phenomenon where white light splits into its seven constituent colors (VIBGYOR) when passing through a prism due to different refractive indices for different wavelengths.
Q10. The instrument used to measure electric potential difference (voltage) is a:
(a) Ammeter
(b) Voltmeter
(c) Galvanometer
(d) Ohmmeter
Answer: (b)
Explanation: A voltmeter measures potential difference and is always connected in parallel across the component. An ammeter measures current, and an ohmmeter measures resistance.
Q11. Which energy conversion takes place in a dry cell (battery)?
(a) Electrical energy to Chemical energy
(b) Chemical energy to Electrical energy
(c) Mechanical energy to Electrical energy
(d) Electrical energy to Mechanical energy
Answer: (b)
Explanation: A dry cell or battery converts stored chemical energy into electrical energy through chemical reactions.
Q12. The magnetic field lines outside a bar magnet emerge from which pole and merge into which pole?
(a) Emerge from North, merge into South
(b) Emerge from South, merge into North
(c) Emerge from East, merge into West
(d) Emerge from West, merge into East
Answer: (a)
Explanation: Outside a bar magnet, magnetic field lines originate from the North pole and terminate at the South pole, forming continuous closed loops.
Q13. Superconductors are materials that offer:
(a) Very high resistance
(b) Zero resistance
(c) High resistance at low temperatures
(d) Low resistance at high temperatures
Answer: (b)
Explanation: Superconductors are materials that, when cooled below a critical temperature, exhibit exactly zero electrical resistance and expel magnetic fields (Meissner effect).
Q14. The SI unit of work is:
(a) Watt
(b) Joule
(c) Newton
(d) Pascal
Answer: (b)
Explanation: Work is done when a force causes displacement. The SI unit of work and energy is the Joule (J).
Q15. The acceleration due to gravity on the surface of the Earth is approximately:
(a) 9.8 m/s²
(b) 98 m/s²
(c) 980 m/s²
(d) 0.98 m/s²
Answer: (a)
Explanation: The standard value for the acceleration due to gravity (g) at the Earth’s surface is approximately 9.8 m/s².
Q16. What is the total resistance of two resistors, R1 and R2, connected in series?
(a) (R1 × R2) / (R1 + R2)
(b) R1 + R2
(c) R1 – R2
(d) R1 / R2
Answer: (b)
Explanation: When resistors are connected in series, the total equivalent resistance is the sum of their individual resistances: R_total = R1 + R2.
Q17. The twinkling of stars is primarily due to:
(a) Reflection of light by atmospheric dust
(b) Dispersion of light by water droplets
(c) Atmospheric refraction of starlight
(d) Absorption of light by the atmosphere
Answer: (c)
Explanation: The twinkling of stars is caused by the continuous change in the refractive index of the Earth’s atmosphere, which leads to varying amounts of starlight reaching our eyes.
Q18. Which type of lens is used to correct myopia (nearsightedness)?
(a) Convex lens
(b) Concave lens
(c) Cylindrical lens
(d) Biconvex lens
Answer: (b)
Explanation: Myopia is a vision defect where a person can see nearby objects clearly but distant objects appear blurred. It is corrected by using a concave lens, which diverges light rays before they reach the eye.
Q19. The principle of working of a rocket is based on:
(a) Newton’s First Law of Motion
(b) Newton’s Second Law of Motion
(c) Newton’s Third Law of Motion
(d) Law of Conservation of Energy
Answer: (c)
Explanation: Rockets operate on Newton’s Third Law of Motion: “For every action, there is an equal and opposite reaction.” The expulsion of high-velocity gases creates an equal and opposite thrust that propels the rocket forward.
Q20. In an AC generator, what converts AC current into DC current?
(a) Slip rings
(b) Commutator (split rings)
(c) Brushes
(d) Armature
Answer: (b)
Explanation: An AC generator produces alternating current. To convert this to direct current, a commutator (split ring) is used in a DC generator to reverse the current direction in the external circuit every half rotation.
Q21. What is the SI unit of frequency?
(a) Meter
(b) Second
(c) Hertz
(d) Radian
Answer: (c)
Explanation: Frequency is the number of cycles or oscillations per unit time. Its SI unit is Hertz (Hz), which is equivalent to cycles per second.
Q22. An object placed at the center of curvature of a concave mirror will form an image that is:
(a) Real, inverted, and smaller than the object
(b) Real, inverted, and same size as the object
(c) Virtual, upright, and larger than the object
(d) Real, inverted, and larger than the object
Answer: (b)
Explanation: When an object is placed at the center of curvature (C) of a concave mirror, the image formed is real, inverted, and of the same size as the object, located also at C.
Q23. The energy possessed by a body due to its motion is called:
(a) Potential energy
(b) Kinetic energy
(c) Mechanical energy
(d) Thermal energy
Answer: (b)
Explanation: Kinetic energy is the energy an object possesses due to its motion. Potential energy is due to its position or state.
Q24. Which of the following is a non-renewable source of energy?
(a) Solar energy
(b) Wind energy
(c) Coal
(d) Hydroelectric energy
Answer: (c)
Explanation: Non-renewable energy sources are natural resources that cannot be replaced after they are used up. Coal is a fossil fuel and a non-renewable source. Solar, wind, and hydroelectric are renewable.
Q25. The phenomenon responsible for the blue color of the sky is:
(a) Reflection
(b) Refraction
(c) Dispersion
(d) Scattering
Answer: (d)
Explanation: The blue color of the sky is due to Rayleigh scattering. Shorter wavelengths (like blue light) are scattered more effectively by the molecules in the Earth’s atmosphere than longer wavelengths (like red light).
