Railway 2024 Previous Year GK Questions with Answers

The correct answer is D, Fleming's Left-Hand Rule. It gives the direction of the force, and so of the motion, on a current-carrying conductor placed in a magnetic field, which is exactly what turns the coil of a motor. Stretch the thumb, forefinger and middle finger of the left hand so that they are at right angles to one another. If the forefinger points along the magnetic field and the middle finger along the current, the thumb points in the direction of the force. The force is greatest when the current is at right angles to the field. A is wrong because Ampere's law relates the magnetic field around a closed loop to the current passing through it. B is wrong because the right-hand thumb rule finds the direction of the magnetic field lines around a straight current-carrying wire. C is wrong because Fleming's right-hand rule gives the direction of the induced current in a generator. Exam tip: left hand for motor, right hand for generator; forefinger = field, middle finger = current, thumb = motion.

The correct answer is A, CH₄ + 2O₂ → CO₂ + 2H₂O. Combustion means burning in oxygen, and complete burning of methane gives carbon dioxide, water, heat and light. The equation is balanced: one carbon, four hydrogen and four oxygen atoms on each side. Methane is the simplest hydrocarbon and the main gas in natural gas, CNG and biogas, which is why it burns with a clean blue flame in stoves and vehicles. When oxygen is short, burning is incomplete and poisonous carbon monoxide forms instead of carbon dioxide. B is wrong because it is a substitution reaction: in sunlight chlorine replaces a hydrogen atom of methane, and nothing burns. C is wrong because it is not balanced and shows carbon monoxide, the product of incomplete burning. D is wrong because methane reacting with steam, not oxygen, to give carbon monoxide and hydrogen is steam reforming, an industrial way to make hydrogen. Exam tip: complete combustion of any hydrocarbon gives CO₂ + H₂O + energy.