Electricity, Light and Sound MCQs

Solved Everyday Science MCQs on electricity (conductors, fuses, AC, transformers, kWh), light (refraction, scattering, optical fibre) and sound (echo, ultrasound).

1. 1

   Which of the following is a good conductor of electricity?

   ACopperBDry woodCGlassDRubber

   Correct answer: A. Copper

   Copper conducts electricity well, which is why it is used in wires. Rubber, glass and dry wood are insulators.

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2. 2

   A fuse in an electric circuit protects it by:

   AIncreasing the voltageBMelting and breaking the circuit when too much current flowsCConverting AC to DCDStoring extra electricity

   Correct answer: B. Melting and breaking the circuit when too much current flows

   A fuse wire has a low melting point. If the current becomes dangerously high, it melts and stops the flow.

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3. 3

   The frequency of the alternating current (AC) supply in Pakistan is:

   A50 HzB60 HzC100 HzD220 Hz

   Correct answer: A. 50 Hz

   Pakistan's mains supply is about 230 volts at 50 hertz. Some countries, such as the USA, use 60 Hz.

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4. 4

   A device used to increase or decrease AC voltage is called a:

   ATransformerBGeneratorCRectifierDMotor

   Correct answer: A. Transformer

   Transformers step voltage up for long-distance transmission and down for safe use in homes.

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5. 5

   An electric generator converts:

   AChemical energy into heatBElectrical energy into mechanical energyCHeat into lightDMechanical energy into electrical energy

   Correct answer: D. Mechanical energy into electrical energy

   Generators turn the motion of turbines (driven by water, steam or wind) into electricity. An electric motor does the reverse.

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6. 6

   An electric motor converts:

   ALight into electricityBSound into electricityCElectrical energy into mechanical energyDMechanical energy into electrical energy

   Correct answer: C. Electrical energy into mechanical energy

   Motors in fans, pumps and washing machines turn electrical energy into motion.

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7. 7

   Electromagnetic induction, the principle behind generators and transformers, was discovered by:

   AThomas EdisonBNikola TeslaCAlessandro VoltaDMichael Faraday

   Correct answer: D. Michael Faraday

   Michael Faraday showed in 1831 that a changing magnetic field can produce an electric current.

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8. 8

   Electricity bills measure the energy used in:

   AAmperesBKilowatt-hours (units)CVoltsDWatts

   Correct answer: B. Kilowatt-hours (units)

   One kilowatt-hour (one "unit") is the energy used by a 1,000-watt appliance running for one hour.

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9. 9

   How are appliances in a house normally connected to the mains supply?

   AIn seriesBRandomlyCIn parallelDIn a single loop

   Correct answer: C. In parallel

   Parallel connection gives every appliance the full mains voltage and lets each be switched on or off independently.

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10. 10

    The material most widely used to make computer chips and solar cells is:

    AIronBSiliconCCopperDAluminium

    Correct answer: B. Silicon

    Silicon is a semiconductor: its conductivity can be controlled, which makes it ideal for electronic components.

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12. 11

    The purpose of earthing (grounding) an electrical appliance is to:

    AProtect users from electric shockBReduce noiseCSave electricityDIncrease brightness

    Correct answer: A. Protect users from electric shock

    If a fault makes the appliance's metal body live, the earth wire carries the current safely into the ground.

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13. 12

    A pencil placed in a glass of water appears bent because of:

    ADispersionBReflectionCRefractionDDiffraction

    Correct answer: C. Refraction

    Light bends (refracts) as it passes from water into air, so the submerged part of the pencil appears shifted.

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14. 13

    Optical fibres carry light signals over long distances using:

    ADiffractionBTotal internal reflectionCRefraction onlyDAbsorption

    Correct answer: B. Total internal reflection

    Light hitting the inside of the fibre at a steep angle reflects completely, so it stays trapped inside as it travels.

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15. 14

    The sky appears blue mainly because:

    AAir molecules scatter blue light more than red lightBOzone is blueCThe ocean reflects onto itDClouds absorb red light

    Correct answer: A. Air molecules scatter blue light more than red light

    Shorter blue wavelengths are scattered much more by air molecules, filling the sky with blue light.

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16. 15

    A mirage seen on a hot road is caused by:

    AReflection from waterBDispersion by raindropsCDust in the airDRefraction of light through layers of hot and cooler air

    Correct answer: D. Refraction of light through layers of hot and cooler air

    Light bends as it passes through air of different temperatures, creating the illusion of water on the road.

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17. 16

    The primary colours of light are:

    ARed, white and blackBRed, green and blueCRed, yellow and blueDCyan, magenta and yellow

    Correct answer: B. Red, green and blue

    Red, green and blue light combine to make white light, and screens use them to make all other colours.

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18. 17

    In which medium does light travel the fastest?

    AWaterBDiamondCGlassDVacuum

    Correct answer: D. Vacuum

    Light travels fastest in a vacuum (about 3 × 10⁸ m/s) and slows down in materials such as water and glass.

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19. 18

    An echo is produced by the:

    ARefraction of soundBAbsorption of soundCDispersion of soundDReflection of sound

    Correct answer: D. Reflection of sound

    An echo is a sound reflected back from a large surface such as a cliff or a wall.

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20. 19

    The normal range of human hearing is approximately:

    A2 Hz to 2,000 HzB20 Hz to 20,000 HzC200 Hz to 200,000 HzD20,000 Hz and above

    Correct answer: B. 20 Hz to 20,000 Hz

    Humans hear roughly from 20 Hz to 20 kHz. The upper limit falls with age.

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21. 20

    Sound waves with frequencies above the range of human hearing (above about 20,000 Hz) are called:

    AUltrasoundBRadio wavesCInfrasoundDSupersonic

    Correct answer: A. Ultrasound

    Ultrasound is used in medical scans and by animals such as bats. Infrasound lies below 20 Hz.

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