NDA GK Questions 2026

LFP cells are prized for safety, long cycle life and the absence of cobalt, which makes them cheaper and less exposed to supply disruption; their weakness is a lower energy density, so a pack of the same range weighs more.

The layered structure of graphite can accept lithium ions between its sheets, a process called intercalation, and release them again without breaking down, which is what makes the cell rechargeable over hundreds of cycles.

Whittingham built the first working lithium cell in the 1970s, Goodenough found that a lithium cobalt oxide cathode could give a far higher voltage, and Yoshino replaced the dangerous metallic lithium anode with a carbon material, producing the safe, rechargeable cell that was commercialised in 1991.

A BEV carries no engine at all; it runs entirely on a traction battery that is charged from an external electricity supply, and it has no tailpipe emissions.

This is a glucose analogue in which fluorine-18 replaces a hydroxyl group.

It regulates the use of pre-natal diagnostic techniques, requires every ultrasound clinic to be registered and to keep records, and prohibits sex selection before or after conception as well as the communication of the sex of the foetus to anyone.

Gadolinium is a rare earth element whose ion is strongly paramagnetic, so it shortens the relaxation time of nearby hydrogen nuclei and brightens the tissue it reaches.

Hounsfield, an engineer at EMI in Britain, built the first clinical CT scanner, and Cormack, a physicist, had independently worked out the mathematics of reconstructing a cross-section from measurements taken along many directions.

When sound is reflected from a moving target, the frequency of the echo is shifted: higher when the blood is moving towards the probe and lower when it is moving away.

Certain crystals develop a voltage across their faces when they are mechanically squeezed, and conversely change shape when a voltage is applied.

The tesla is the SI unit of magnetic flux density, and clinical MRI scanners commonly work at one and a half or three tesla, produced by a superconducting coil kept cold by liquid helium.

A single proton, the nucleus of ordinary hydrogen, has a spin and therefore a magnetic moment, and hydrogen is by far the most abundant such nucleus in the body because the body is largely water and fat.

The cutoff or minimum wavelength of the continuous X-ray spectrum arises when an electron gives up its entire kinetic energy in a single collision with the target.

The Hounsfield unit, named after Godfrey Hounsfield, expresses how strongly a small volume of tissue attenuates X-rays, on a scale fixed by definition at zero for water and minus one thousand for air.

MRI works by placing the hydrogen nuclei of the body in a strong static magnetic field and disturbing them with radiofrequency pulses, which lie in the harmless low-energy part of the electromagnetic spectrum.

Working with a discharge tube at the University of Wurzburg in November 1895, Roentgen noticed that a screen coated with a fluorescent salt glowed even when the tube was covered, and he traced the effect to an unknown penetrating radiation that he called X-radiation.

A homolographic or equal-area projection keeps the ratio of areas on the map the same as on the globe, which is why world distribution maps of population, crops or forests are drawn on projections such as Mollweide's or the sinusoidal.

A cadastral map is a very large-scale map of a village or a town drawn to register plots, fields, their boundaries and their owners, and it is the basis of land revenue records and of the registration of property.

It is usually expressed as the ground size of one pixel, so a sensor of one metre resolution can separate objects about a metre across, which is what makes high-resolution imagery useful for urban mapping.

The National Remote Sensing Centre, a centre of the Indian Space Research Organisation, works from Hyderabad and operates the earth station at Shadnagar nearby, where data from Indian and foreign satellites is received.