General Science MCQs – Page 99 (Q981-990)

The sharpness or overall level of visual detail present in a digital photo is commonly described in terms of the total number of individual pixels, or picture elements, it contains, with a photo generally described as having higher resolution, and correspondingly greater potential fine visual detail, when it is composed of a considerably larger total number of these individual pixels. A digital camera's overall resolution is frequently advertised and marketed in megapixels, with one full megapixel equaling exactly one million individual pixels, and while higher resolution generally allows for meaningfully greater image detail, actual final image quality also depends significantly on several other important factors, including the camera's specific lens quality and sensor size.

A hybrid car is generally powered by a combination of a traditional internal combustion engine and an electric motor and battery, intelligently switching between these two distinct available power sources, or in many designs actively and seamlessly combining them together, specifically to help meaningfully improve overall fuel efficiency and correspondingly reduce total harmful vehicle emissions compared to conventional gasoline-only vehicles. Many modern hybrid vehicles also employ regenerative braking technology, a clever process that captures and usefully recovers a portion of the vehicle's kinetic energy during braking and subsequently converts it back into usable stored electrical energy for later reuse.

Fully electric vehicles are generally powered primarily by rechargeable batteries, most commonly modern lithium-ion battery technology, which store substantial electrical energy that is subsequently used to directly power one or more electric motors responsible for actually driving the vehicle's wheels, entirely without requiring any traditional internal combustion engine or gasoline fuel whatsoever. Electric vehicles generally produce genuinely zero direct tailpipe emissions during actual everyday operation, though their overall total environmental impact still ultimately depends significantly on the specific original source of the electricity used to charge their batteries in the first place.

An electric fan generally converts electrical energy into mechanical, rotational energy to move air, using an internal electric motor that reliably converts the incoming supplied electrical current into rotational mechanical motion, causing the fan's angled blades to spin rapidly and thereby push and circulate surrounding air forward. This moving air subsequently helps meaningfully cool people by accelerating natural evaporative cooling of sweat directly from the skin's surface, even though the fan itself technically does not actually lower the surrounding room's overall air temperature in any way, since fans work purely through improved air circulation and evaporation rather than genuinely refrigerating or cooling the air itself.

Modern elevators and escalators generally rely mainly on motor-driven mechanical systems to reliably move people efficiently between different building levels, using powerful electric motors combined with strong steel cables, pulleys, and counterweights, in the specific case of elevators, or continuously moving stepped conveyor belt mechanisms, in the specific case of escalators, to provide smooth, safe, and consistently reliable vertical or inclined transportation. These well-established mechanical systems incorporate numerous important safety features, including backup emergency braking systems, specifically designed to help reliably prevent dangerous accidents even in the unlikely event of an unexpected power failure or mechanical malfunction.

Digital clinical thermometers commonly used today generally measure human body temperature using an electronic temperature sensor, typically a small thermistor whose measurable electrical resistance reliably and predictably changes in direct, precise response to changing temperature, allowing the connected internal digital circuitry to accurately and quickly calculate and clearly display the corresponding measured body temperature reading. These modern digital thermometers offer several genuine practical advantages over older traditional mercury thermometers, including notably faster measurement readings, improved overall measurement safety, and the complete elimination of any potential risk from toxic mercury exposure or accidental spillage.

Older dial-up internet connections historically relied on a device called a modem mainly to convert a computer's outgoing digital data into corresponding audio signals genuinely capable of being transmitted over standard analog telephone lines, and then correspondingly convert incoming received analog audio signals back into usable digital data once again. The specific term modem itself is actually a practical shortened contraction combining the two words modulator and demodulator, precisely and accurately describing this essential dual conversion function, and dial-up internet connections were notably quite slow by modern standards and famously tied up the household telephone line entirely whenever actively in active use.

PDF generally stands for Portable Document Format, a widely used, genuinely versatile digital file format specifically developed by Adobe in 1993 and deliberately designed to reliably preserve a document's precise original formatting, fonts, and overall visual layout consistently across many different computer devices, operating systems, and various different software programs. This particular platform-independent design characteristic has made PDF files genuinely extremely popular and widely used for reliably sharing official documents, forms, and various other important printed materials, since a properly created PDF file will reliably and consistently look exactly the same regardless of the specific device or software actually used to open and view it.

USB generally stands for Universal Serial Bus, a widely adopted, genuinely standardized technology used to reliably connect a remarkably wide range of different external devices, including keyboards, mice, printers, and portable external storage drives, to computers and countless other electronic devices. Before USB became so widely standardized and universally adopted, connecting different external devices to a computer often genuinely required numerous different specialized, often mutually incompatible connector types, and USB's now-widespread universal adoption has significantly simplified overall device connectivity while also conveniently enabling both reliable data transfer and direct electrical power delivery through the very same single standardized cable.

Kevlar, a strong, remarkably lightweight synthetic fiber developed by chemist Stephanie Kwolek in 1965, is widely known and valued for its extensive use in manufacturing effective bulletproof vests, since its unique molecular structure provides genuinely exceptional tensile strength significantly exceeding that of steel when measured on an equivalent weight basis, allowing it to effectively absorb and safely dissipate the very high kinetic energy of an incoming bullet impact. Beyond its well-known protective body armor applications, Kevlar is also very widely used in numerous other demanding applications requiring its combination of high strength and light weight, including racing tires, various protective sporting equipment, and select aerospace components.