Read each question, consider the options, then reveal the correct answer and explanation.
Incandescent electric light bulbs are typically filled with an inert gas, most commonly nitrogen (sometimes combined with argon), rather than ordinary air, because this prevents the hot tungsten filament inside from reacting with oxygen and burning out prematurely.
Normal blood pressure for a healthy adult is typically around 120/80 mmHg, where 120 represents the systolic pressure (the force when the heart contracts and pumps blood) and 80 represents the diastolic pressure (the force when the heart rests between beats).
Solar plates, also known as solar panels, are composed of photovoltaic (PV) cells. These cells convert sunlight directly into electricity through the photovoltaic effect. Fuel cells generate electricity through a chemical reaction, not directly from sunlight.
The phases of the moon are caused by the relative positions of the Earth, the Moon, and the Sun. As the Moon orbits the Earth, different portions of its sunlit side become visible to us. The moon itself does not change; only the angle of illumination changes.
Granite is classified as an igneous rock, meaning it forms from the slow cooling and solidification of molten magma beneath the Earth's surface, resulting in its characteristic coarse-grained, crystalline texture composed mainly of quartz, feldspar, and mica.
Vegetable ghee (or vanaspati) is made by hydrogenating vegetable oil. Hydrogenation is a chemical reaction where hydrogen is added to the unsaturated oils, making them more saturated and solid at room temperature. This process also makes the oil more stable.
Hydrogen gas is highly combustible (flammable), readily reacting with oxygen in an exothermic reaction to produce water and release energy, which is why it has been explored and used as a fuel source, despite the safety precautions its flammability requires.
Johannes Kepler, a German astronomer and mathematician, formulated the three laws of planetary motion in the early 17th century, describing how planets move in elliptical orbits around the sun, building on earlier observational data collected by Tycho Brahe.
The boiling point of water is directly dependent on atmospheric pressure: at higher altitudes, where atmospheric pressure is lower, water boils at a lower temperature, while at sea level, where pressure is higher, water boils at the standard 100°C (212°F).
Venus is the hottest planet in our solar system due to its thick atmosphere of carbon dioxide, which creates a runaway greenhouse effect. The average surface temperature on Venus is around 462°C, hotter than Mercury despite Mercury being closer to the sun.
