The handle of a door is usually placed as far as possible from the hinges to provide a:
A. Larger force
B. Smaller moment
C. Larger moment
D. Smaller friction
Answer: C. Larger moment
Explanation: Moment = Force * perpendicular distance. Increasing the distance makes it easier to turn the door with less effort.
Question 10
A bullet of mass 0.02kg is fired from a gun of mass 4kg. If the bullet leaves with a velocity of 200 m/s, calculate the recoil velocity of the gun.
A. 1.0 m/s
B. 0.1 m/s
C. 4.0 m/s
D. 10.0 m/s
Answer: A. 1.0 m/s
Explanation: (Mass of gun * Recoil velocity) = (Mass of bullet * Bullet velocity). 4 * V = 0.02 * 200. 4V = 4. V = 1.0 m/s.
Question 11
Which of the following materials is most elastic?
A. Rubber
B. Steel
C. Glass
D. Plasticine
Answer: B. Steel
Explanation: In physics, elasticity is measured by the ability to return to original shape after high stress. Steel has a much higher Young's Modulus than rubber.
Question 12
Upthrust on a body fully immersed in a liquid depends on the:
A. Weight of the body
B. Density of the body
C. Density of the liquid
D. Mass of the body
Answer: C. Density of the liquid
Explanation: Upthrust = Volume of liquid displaced * density of liquid * g.
Question 13
The pressure at a depth of 20m in water is P. What is the pressure at a depth of 20m in a liquid whose density is twice that of water?
A. P
B. 2P
C. 0.5P
D. 4P
Answer: B. 2P
Explanation: Pressure P = h * rho * g. If density (rho) doubles, pressure doubles for the same depth.
Question 14
The anomalous expansion of water occurs between:
A. -4 and 0 degrees C
B. 0 and 4 degrees C
C. 4 and 100 degrees C
D. 0 and 100 degrees C
Answer: B. 0 and 4 degrees C
Explanation: In this range, water contracts when heated and expands when cooled.
Question 15
Which of the following thermometers is used to measure very high temperatures, such as in a furnace?
A. Clinical thermometer
B. Alcohol thermometer
C. Optical pyrometer
D. Mercury-in-glass thermometer
Answer: C. Optical pyrometer
Explanation: Pyrometers measure heat by the intensity of light/radiation emitted by the hot object.
Question 16
The heat required to change the state of 1kg of a substance without a change in temperature is:
A. Specific heat capacity
B. Latent heat
C. Heat capacity
D. Internal energy
Answer: B. Latent heat
Explanation: "Latent" means hidden. This energy is used to break bonds during a phase change.
Question 17
A gas occupies 500 cm^3 at 27 degrees C. At what temperature will it occupy 1000 cm^3 at constant pressure?
A. 54 degrees C
B. 600 degrees C
C. 327 degrees C
D. 127 degrees C
Answer: C. 327 degrees C
Explanation: Using V1/T1 = V2/T2. Convert to Kelvin: T1 = 300K. 500/300 = 1000/T2. T2 = 600K. 600K - 273 = 327 degrees C.
Question 18
The process of heat transfer in a vacuum is:
A. Conduction
B. Convection
C. Radiation
D. Evaporation
Answer: C. Radiation
Explanation: Radiation does not require a material medium.
Question 19
Specific heat capacity is measured in:
A. J/kg
B. J/K
C. J/kg/K
D. kg/J/K
Answer: C. J/kg/K
Explanation: c = Q / (m * delta theta). Unit = Joule / (kg * Kelvin).
Question 20
The smell of perfume spreading across a room is an evidence of:
A. Osmosis
B. Diffusion
C. Brownian motion
D. Capillarity
Answer: B. Diffusion
Explanation: Diffusion is the movement of particles from a region of higher concentration to lower concentration.
Question 21
Which of the following waves requires a material medium for propagation?
A. Light waves
B. Radio waves
C. Sound waves
D. X-rays
Answer: C. Sound waves
Explanation: Sound is a mechanical wave and cannot travel through a vacuum.
Question 22
The image formed by a plane mirror is always:
A. Real, upright and same size
B. Virtual, inverted and same size
C. Virtual, upright and same size
D. Real, inverted and diminished
Answer: C. Virtual, upright and same size
Explanation: Plane mirror images cannot be caught on a screen (virtual) and are laterally inverted but upright.
Question 23
Calculate the refractive index of a medium if the speed of light in it is 2.0 x 10^8 m/s. (Speed of light in vacuum = 3.0 x 10^8 m/s)
A. 0.67
B. 1.50
C. 1.33
D. 2.00
Answer: B. 1.50
Explanation: Refractive index n = c / v. n = 3.0 / 2.0 = 1.5.
Question 24
The defect of the eye where a person sees far objects clearly but cannot see near objects is:
A. Myopia
B. Hypermetropia
C. Astigmatism
D. Cataract
Answer: B. Hypermetropia
Explanation: Also known as long-sightedness. It is corrected with a convex (converging) lens.
Question 25
Which of the following is a stringed instrument?
A. Flute
B. Drum
C. Violin
D. Trumpet
Answer: C. Violin
Explanation: Stringed instruments produce sound through the vibration of stretched strings.
Question 26
The loudness of sound is most closely related to its:
A. Frequency
B. Amplitude
C. Wavelength
D. Pitch
Answer: B. Amplitude
Explanation: Larger amplitude waves carry more energy and sound louder.
Question 27
The fundamental frequency of a closed pipe of length L is:
A. v / 2L
B. v / 4L
C. 2v / L
D. v / L
Answer: B. v / 4L
Explanation: In a closed pipe, the wavelength of the fundamental mode is 4 times the length of the pipe.
Question 28
When light passes from air into water, its frequency:
A. Increases
B. Decreases
C. Remains constant
D. Becomes zero
Answer: C. Remains constant
Explanation: During refraction, the speed and wavelength change, but the frequency depends only on the source and stays the same.
Question 29
A convex lens has a focal length of 10cm. Calculate its power.
A. 0.1 D
B. 10.0 D
C. 1.0 D
D. 5.0 D
Answer: B. 10.0 D
Explanation: Power P = 1 / f (in meters). f = 0.1m. P = 1 / 0.1 = 10 Dioptres.
Question 30
The color of light with the shortest wavelength in the visible spectrum is:
A. Red
B. Yellow
C. Blue
D. Violet
Answer: D. Violet
Explanation: Violet has the highest frequency and shortest wavelength. Red has the longest.
Question 31
The unit of electric potential difference is the:
A. Ampere
B. Ohm
C. Volt
D. Coulomb
Answer: C. Volt
Explanation: Volt is defined as one Joule per Coulomb.
Question 32
Three 4-ohm resistors are connected in series. What is the effective resistance?
A. 1.33 ohms
B. 4.00 ohms
C. 12.00 ohms
D. 0.75 ohm
Answer: C. 12.00 ohms
Explanation: For series connection, R = R1 + R2 + R3 = 4 + 4 + 4 = 12 ohms.
Question 33
A device used to store electric charge is a:
A. Resistor
B. Inductor
C. Capacitor
D. Diode
Answer: C. Capacitor
Explanation: Capacitors store energy in an electric field between two plates.
Question 34
The resistance of a conductor is 10 ohms. If a potential difference of 20V is applied, calculate the current.
A. 200 A
B. 0.5 A
C. 2.0 A
D. 10.0 A
Answer: C. 2.0 A
Explanation: I = V / R. I = 20 / 10 = 2 Amperes.
Question 35
The part of an AC generator that conducts current to the external circuit is the:
A. Commutator
B. Slip rings and brushes
C. Armature
D. Field magnet
Answer: B. Slip rings and brushes
Explanation: Slip rings allow the coil to rotate while maintaining electrical contact via the brushes.
Question 36
The magnetic field lines around a straight current-carrying wire are:
A. Straight lines parallel to the wire
B. Concentric circles
C. Radial lines
D. Elliptical loops
Answer: B. Concentric circles
Explanation: The direction is found using the Right-Hand Grip Rule.
Question 37
A step-up transformer has a primary coil of 100 turns and a secondary coil of 500 turns. If the input voltage is 20V, find the output voltage.
A. 100 V
B. 4 V
C. 200 V
D. 50 V
Answer: A. 100 V
Explanation: Vs / Vp = Ns / Np. Vs / 20 = 500 / 100. Vs = 20 * 5 = 100 Volts.
Question 38
Which of the following is an example of a "hard" magnetic material?
A. Soft iron
B. Steel
C. Nickel
D. Copper
Answer: B. Steel
Explanation: Hard magnetic materials are difficult to magnetize but retain their magnetism for a long time.
Question 39
The process of adding an impurity to a semiconductor to increase its conductivity is:
A. Doping
B. Rectification
C. Ionization
D. Polarization
Answer: A. Doping
Explanation: Doping creates n-type or p-type semiconductors.
Question 40
A semiconductor diode conducts current when it is:
A. Reverse biased
B. Forward biased
C. Not biased
D. Overheated
Answer: B. Forward biased
Explanation: Forward biasing reduces the depletion layer width, allowing current to flow.
Question 41
Cathode rays consist of fast-moving:
A. Protons
B. Neutrons
C. Electrons
D. Photons
Answer: C. Electrons
Explanation: Cathode rays are streams of electrons observed in vacuum tubes.
Question 42
The particle emitted in a radioactive decay that has a negative charge is the:
A. Alpha particle
B. Beta particle
C. Gamma ray
D. Positron
Answer: B. Beta particle
Explanation: A beta-minus particle is an electron.
Question 43
A radioactive substance has a half-life of 10 minutes. If 100g is present initially, how much remains after 30 minutes?
A. 50.0 g
B. 25.0 g
C. 12.5 g
D. 6.25 g
Answer: C. 12.5 g
Explanation: 30 minutes = 3 half-lives. Mass = 100 / (2^3) = 100 / 8 = 12.5g.
Question 44
Which radiation has the least ionizing power but the highest penetrating power?
A. Alpha particles
B. Beta particles
C. Gamma rays
D. X-rays
Answer: C. Gamma rays
Explanation: Gamma rays have no charge or mass, allowing them to pass through materials easily but interact less with atoms.
Question 45
The process of splitting a heavy nucleus into two smaller nuclei is:
A. Nuclear fusion
B. Nuclear fission
C. Radioactive decay
D. Thermionic emission
Answer: B. Nuclear fission
Explanation: This is the principle behind nuclear power plants and atomic bombs.
Question 46
Which of the following is a primary source of energy in the sun?
A. Fission of Uranium
B. Fusion of Hydrogen
C. Combustion of coal
D. Fission of Helium
Answer: B. Fusion of Hydrogen
Explanation: Hydrogen nuclei fuse to form Helium, releasing massive energy.
Question 47
Calculate the energy of a photon of light with a frequency of 5.0 x 10^14 Hz. (h = 6.6 x 10^-34 Js)
A. 3.3 x 10^-19 J
B. 1.3 x 10^-19 J
C. 3.3 x 10^48 J
D. 3.3 x 10^-48 J
Answer: A. 3.3 x 10^-19 J
Explanation: E = h * f. E = (6.6 x 10^-34) * (5.0 x 10^14) = 33 x 10^-20 = 3.3 x 10^-19 Joules.
Question 48
A p-type semiconductor is obtained by doping a pure semiconductor with a ______ element.
A. Group 2
B. Group 3
C. Group 4
D. Group 5
Answer: B. Group 3
Explanation: Group 3 elements (trivalent) create "holes" which act as positive charge carriers.
Question 49
The stopping potential in a photoelectric experiment depends on the:
A. Intensity of light
B. Surface area of the metal
C. Frequency of light
D. Time of exposure
Answer: C. Frequency of light
Explanation: Stopping potential is proportional to the maximum kinetic energy of the electrons, which is determined by frequency.
Question 50
The time taken for a satellite to complete one orbit around the Earth is its:
A. Velocity
B. Period
C. Acceleration
D. Range
Answer: B. Period
Explanation: Period is the time for one full revolution or cycle.