Energy (including Heat Transfer) Quiz - ICSE Class 8 Science
Free practice quiz: Energy (including Heat Transfer) (ICSE Class 8 Science). 49 multiple-choice questions with answers and explanations. Play online, no sign-up needed.
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When sunlight falls on a black cloth and a white cloth kept side by side, the black cloth becomes hotter. This is because the black cloth:
- reflects more heat radiation
- absorbs more heat radiation
- conducts heat better
- convects heat better
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Answer: B. absorbs more heat radiation
Dark-colored surfaces, especially black, are good absorbers of heat radiation (like sunlight). White and light-colored surfaces are good reflectors of heat radiation. When the black cloth absorbs more heat radiation from the sun, its temperature increases more than the white cloth, which reflects most of the radiation.
When water is heated in a pot on a stove, the water at the bottom gets hot first and then rises, while the cooler water from the top sinks. This process of heat transfer is called:
- Conduction
- Radiation
- Convection
- Absorption
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Answer: C. Convection
This describes the formation of convection currents. As the water at the bottom heats up, it becomes less dense and rises. Cooler, denser water from the top sinks to take its place, gets heated, and rises, creating a continuous cycle of heat transfer within the water.
A metal rod is heated at one end. After some time, the other end also becomes hot. This transfer of heat through the solid rod is primarily due to:
- Convection
- Radiation
- Conduction
- Diffusion
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Answer: C. Conduction
In solids, heat transfer primarily occurs through conduction. The heat energy causes the atoms or molecules at the heated end to vibrate more vigorously, and these vibrations are passed along to adjacent particles, transferring heat throughout the rod.
A power plant burns coal to produce electricity. This is an example of converting energy from one form to another. What is the sequence of primary energy conversions?
- Chemical Energy → Kinetic Energy → Electrical Energy
- Chemical Energy → Thermal Energy → Mechanical Energy → Electrical Energy
- Thermal Energy → Chemical Energy → Electrical Energy
- Mechanical Energy → Thermal Energy → Electrical Energy
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Answer: B. Chemical Energy → Thermal Energy → Mechanical Energy → Electrical Energy
Burning coal (chemical energy) produces heat (thermal energy). This heat is used to produce steam, which drives turbines (mechanical energy). The spinning turbines then power generators to produce electricity.
Which of the following scenarios best illustrates the transfer of heat by convection?
- Feeling the warmth of the sun on your skin.
- Touching a hot stove and feeling the heat immediately.
- A sea breeze blowing from the cooler sea to the warmer land.
- A metal spoon becoming hot when placed in hot soup.
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Answer: C. A sea breeze blowing from the cooler sea to the warmer land.
A sea breeze is caused by convection. The land heats up faster than the sea, causing the air above the land to become less dense and rise. Cooler, denser air from the sea then moves in to replace it, creating a breeze. Feeling the sun's warmth is radiation. Touching a hot stove or a metal spoon in soup involves conduction.