Here are 25 multiple-choice questions on Basic Physics, tailored for JKSSB and similar competitive exams, suitable for the Forester Exam’s ‘Basic Science’ section.
Basic Science (Physics) – Multiple Choice Questions
Q1. Which of the following is a scalar quantity?
(a) Velocity
(b) Acceleration
(c) Force
(d) Mass
Answer: (d)
Explanation: Scalar quantities have magnitude only, while vector quantities have both magnitude and direction. Mass is a measure of the amount of matter in an object and has no directional component.
Q2. The S.I. unit of power is:
(a) Joule
(b) Watt
(c) Newton
(d) Pascal
Answer: (b)
Explanation: Power is the rate at which work is done or energy is transferred. Its S.I. unit is the Watt (W), which is equivalent to one Joule per second (J/s).
Q3. What causes a body to continue in its state of rest or of uniform motion in a straight line, unless acted upon by an external force?
(a) Momentum
(b) Impulse
(c) Inertia
(d) Gravity
Answer: (c)
Explanation: This statement is Newton’s First Law of Motion, also known as the Law of Inertia. Inertia is the property of an object to resist changes in its state of motion.
Q4. A moving object has kinetic energy. What is the formula for kinetic energy?
(a) $PE = mgh$
(b) $KE = \frac{1}{2}mv^2$
(c) $W = Fd$
(d) $P = VI$
Answer: (b)
Explanation: Kinetic energy (KE) is the energy possessed by an object due to its motion. The formula is $\frac{1}{2}mv^2$, where ‘m’ is mass and ‘v’ is velocity.
Q5. The phenomenon responsible for the twinkling of stars is:
(a) Dispersion of light
(b) Total internal reflection
(c) Atmospheric refraction
(d) Scattering of light
Answer: (c)
Explanation: The twinkling of stars is caused by atmospheric refraction. As light from a distant star enters the Earth’s atmosphere, it passes through layers of air with varying densities and temperatures, causing it to refract (bend) irregularly, making the star appear to twinkle.
Q6. Which color of light deviates the most when passing through a prism?
(a) Red
(b) Orange
(c) Green
(d) Violet
Answer: (d)
Explanation: When white light passes through a prism, it splits into its constituent colors (VIBGYOR). Violet light has the shortest wavelength and therefore bends the most, while red light has the longest wavelength and bends the least.
Q7. What is the S.I. unit of electric current?
(a) Volt
(b) Ohm
(c) Ampere
(d) Watt
Answer: (c)
Explanation: The S.I. unit of electric current is the Ampere (A). Volt is the unit for potential difference, Ohm for resistance, and Watt for power.
Q8. According to Ohm’s Law, if voltage (V) is applied across a resistor (R), the current (I) flowing through it is given by:
(a) $I = VR$
(b) $I = R/V$
(c) $I = V/R$
(d) $I = V+R$
Answer: (c)
Explanation: Ohm’s Law states that the current flowing through a conductor between two points is directly proportional to the voltage across the two points. The formula is $V = IR$, which can be rearranged to $I = V/R$.
Q9. The instrument used to measure electric potential difference is:
(a) Ammeter
(b) Voltmeter
(c) Galvanometer
(d) Ohmmeter
Answer: (b)
Explanation: A voltmeter is used to measure the potential difference (voltage) between two points in an electrical circuit. An ammeter measures current, a galvanometer detects small currents, and an ohmmeter measures resistance.
Q10. Which type of mirror is used as a rearview mirror in vehicles?
(a) Plane mirror
(b) Concave mirror
(c) Convex mirror
(d) Cylindrical mirror
Answer: (c)
Explanation: Convex mirrors are used as rearview mirrors because they provide a wider field of view and always form erect, diminished images of objects, allowing the driver to see a larger area behind the vehicle.
Q11. The S.I. unit of frequency is:
(a) Meter
(b) Second
(c) Hertz
(d) Radian
Answer: (c)
Explanation: Frequency is the number of occurrences of a repeating event per unit of time. Its S.I. unit is Hertz (Hz), which is equivalent to one cycle per second.
Q12. What is the fundamental reason for the occurrence of seasons on Earth?
(a) Earth’s rotation on its axis
(b) Earth’s elliptical orbit around the Sun
(c) The tilt of Earth’s axis relative to its orbital plane
(d) Changes in the Sun’s activity
Answer: (c)
Explanation: The Earth’s axis is tilted at approximately 23.5 degrees relative to its orbital plane. This tilt causes different parts of the Earth to receive more direct sunlight at different times of the year as it orbits the Sun, leading to the change in seasons.
Q13. Light travels fastest in which of the following media?
(a) Water
(b) Glass
(c) Air
(d) Vacuum
Answer: (d)
Explanation: Light waves do not require a medium to travel and move fastest in a vacuum, where there are no particles to impede their movement. Its speed is approximately $3 \times 10^8$ meters per second in a vacuum.
Q14. The phenomenon of splitting of white light into its constituent colors when passing through a medium like a prism is called:
(a) Reflection
(b) Refraction
(c) Dispersion
(d) Diffraction
Answer: (c)
Explanation: Dispersion is the phenomenon where white light separates into its constituent colors (spectrum) when it passes through a transparent medium like a prism, due to different wavelengths bending at different angles.
Q15. Why does the sky appear blue?
(a) Due to reflection of blue light from oceans
(b) Due to scattering of blue light by atmospheric particles
(c) Due to absorption of other colors of light
(d) Due to the presence of blue colored gases in the atmosphere
Answer: (b)
Explanation: The sky appears blue due to Rayleigh scattering. Shorter wavelengths of light (blue and violet) are scattered more efficiently by the tiny molecules and particles in the Earth’s atmosphere than longer wavelengths (red and yellow).
Q16. Which of the following is a non-renewable source of energy?
(a) Solar energy
(b) Wind energy
(c) Coal
(d) Hydropower
Answer: (c)
Explanation: Non-renewable energy sources are natural resources that cannot be replaced as quickly as they are consumed. Coal, petroleum, and natural gas are examples of non-renewable fossil fuels. Solar, wind, and hydropower are renewable.
Q17. A device that converts electrical energy into mechanical energy is called a:
(a) Generator
(b) Transformer
(c) Motor
(d) Rectifier
Answer: (c)
Explanation: An electric motor converts electrical energy into mechanical energy, typically through the interaction of magnetic fields and current-carrying conductors. A generator does the opposite.
Q18. The S.I. unit of heat is:
(a) Calorie
(b) Joule
(c) Degree Celsius
(d) Kelvin
Answer: (b)
Explanation: Heat is a form of energy. The S.I. unit for all forms of energy, including heat, is the Joule (J). Calorie is another unit for heat, but not the S.I. unit. Degree Celsius and Kelvin are units for temperature.
Q19. What is the principle behind the working of a hydraulic lift?
(a) Bernoulli’s Principle
(b) Archimedes’ Principle
(c) Pascal’s Principle
(d) Newton’s Law of Gravitation
Answer: (c)
Explanation: Pascal’s Principle states that pressure applied to an enclosed incompressible fluid is transmitted undiminished to every portion of the fluid and the walls of the containing vessel. This principle is fundamental to hydraulic systems like lifts and brakes.
Q20. Which of these waves requires a medium for its propagation?
(a) Light waves
(b) Radio waves
(c) Sound waves
(d) X-rays
Answer: (c)
Explanation: Sound waves are mechanical waves, meaning they require a material medium (like air, water, or solids) to travel. Light waves, radio waves, and X-rays are electromagnetic waves, which can travel through a vacuum.
Q21. The phenomenon of light bouncing back when it strikes a smooth, polished surface is called:
(a) Refraction
(b) Dispersion
(c) Reflection
(d) Diffraction
Answer: (c)
Explanation: Reflection is the phenomenon where light rays, upon striking a surface, bounce back from it. This is how mirrors work.
Q22. The S.I. unit of magnetic field strength is:
(a) Weber
(b) Tesla
(c) Henry
(d) Gauss
Answer: (b)
Explanation: The S.I. unit for magnetic field strength (or magnetic flux density) is the Tesla (T). Weber is for magnetic flux, Henry for inductance, and Gauss is a CGS unit for magnetic field.
Q23. If the length of a simple pendulum is doubled, its time period will:
(a) Be halved
(b) Be doubled
(c) Increase by a factor of $\sqrt{2}$
(d) Decrease by a factor of $\sqrt{2}$
Answer: (c)
Explanation: The time period (T) of a simple pendulum is given by the formula $T = 2\pi\sqrt{L/g}$, where L is the length and g is acceleration due to gravity. If L is doubled, T will increase by a factor of $\sqrt{2}$.
Q24. A person standing in front of a plane mirror finds his image to be:
(a) Real, inverted, and same size
(b) Virtual, erect, and magnified
(c) Virtual, erect, and same size
(d) Real, erect, and diminished
Answer: (c)
Explanation: A plane mirror always forms a virtual (cannot be projected on a screen), erect (upright), and same-sized image at the same distance behind the mirror as the object is in front of it.
Q25. What is the S.I. unit of resistance?
(a) Ampere
(b) Volt
(c) Ohm
(d) Farad
Answer: (c)
Explanation: The S.I. unit of electrical resistance is the Ohm ($\Omega$). Ampere is for current, Volt for potential difference, and Farad for capacitance.
