64th Prelims 2018

Explanation:

Both pure water and neutral solutions have a pH of 7. The pH scale ranges from 0 to 14, with lower values indicating acidity and higher values indicating alkalinity. Pure water has equal concentrations of H+ and OH– ions, giving it a neutral pH of 7.

Explanation:

Hydrogen in its most common isotope (protium) does not contain neutrons, only one proton. Other isotopes like deuterium and tritium do contain neutrons. Oxygen, nitrogen, and copper atoms all contain neutrons in their nuclei.

Explanation:

An angstrom (Å) is a unit of length commonly used to measure wavelengths of light and other electromagnetic radiation. 1 Å = 0.1 nanometers or 1×10^-10 meters. It is not used to measure energy, frequency, or velocity.

Explanation:

Frequency is the number of cycles of a periodic event per second. Its SI unit is the Hertz (Hz), named after Heinrich Hertz. One Hertz represents one cycle per second. Meter/second measures velocity, radian measures angles, and watt measures power.

Explanation:

The structure of DNA was discovered by James Watson and Francis Crick. DNA (deoxyribonucleic acid) carries genetic information in all living organisms. Watson and Crick described it as a double helix. Mendel worked on genetics, Johannsen coined the term gene, and Khurrana was a geneticist known for work on nucleic acids.

Explanation:

Triglycerides are the main form of fat in the body and food. They store energy, provide insulation, and protect organs. Proteins are made of amino acids, carbohydrates provide energy, and minerals are inorganic elements needed for body functions.

Explanation:

An electroencephalogram (EEG) records electrical activity in the brain. It is used to diagnose and monitor conditions like epilepsy, sleep disorders, brain injuries, and tumors. It is not used for heart, liver, or pancreas monitoring.

Explanation:

The hypothalamus acts as the body's thermostat. It receives signals from temperature receptors and initiates mechanisms like sweating, vasodilation, shivering, or vasoconstriction to maintain a stable body temperature. Thalamus relays sensory information, cerebellum coordinates movement, and medulla controls autonomic functions.

Explanation:

In the visible spectrum, violet light has the shortest wavelength (~380-450 nm), and red light has the longest (~620-750 nm). Therefore, the wavelength of red light is more than violet light.

Explanation:

To convert Celsius to Fahrenheit: °F = (°C × 9/5) + 32. For 40°C: (40 × 9/5) + 32 = 104°F.

Explanation:

Electric power measures the rate at which electrical energy is consumed or produced. Its SI unit is Watt (W), named after James Watt. Formulas include P = VI or P = I²R.

Explanation:

An electrical motor converts electrical energy into mechanical energy using electromagnetic induction to drive machinery or devices. A generator does the reverse. Electric heaters convert electrical energy to heat.

Explanation:

The human body is composed of approximately 70% water, varying with age, sex, and body composition. Water is essential for cellular function, temperature regulation, nutrient transport, waste removal, and chemical reactions.

Explanation:

An ammeter measures electric current in amperes and is connected in series with a circuit. Voltmeters measure voltage, potentiometers measure potential differences, and hydrometers measure liquid density.

Explanation:

Carbon dioxide (CO2) is the primary greenhouse gas responsible for trapping heat in Earth's atmosphere. Methane, nitrous oxide, and ozone are present in smaller quantities.

Explanation:

Einstein received the 1921 Nobel Prize in Physics for his explanation of the photoelectric effect, which demonstrated the particle nature of light. His theories of relativity did not earn him the Nobel Prize.

Explanation:

Mitochondria produce energy in the form of ATP through cellular respiration. They are called the 'powerhouse' because they generate most of the cell's energy. Cell wall provides structure, ribosomes synthesize proteins, and nucleus stores genetic material.

Explanation:

AIDS (Acquired Immunodeficiency Syndrome) is caused by HIV (Human Immunodeficiency Virus), which attacks the immune system. Bacteria and fungi cause other infections but not AIDS.

Explanation:

A hygrometer measures humidity or water vapor in the air. Hydrometers measure liquid density, pyrometers measure high temperature, and lactometers measure milk density.

Explanation:

Pressure is force per unit area. Its SI unit is Newton per square meter (Pa), also called Pascal. Newton-meter measures torque, Newton measures force, and Newton/meter is used for surface tension.