In a voltaic cell bubbles of hydrogen gas are deposited on one of the plates causing a decrease in the current.
This phenomenon is called
It is observed that in this cell, the current gradually gets reduced and after a certain time of its operation, the current may cease altogether. This decrease of current is due to the deposition of hydrogen on the copper plate. Although the hydrogen comes out from the cell in form of bubbles, but still there is a formation of thin layer on the plate surface. This layer acts as an electrical insulation, thereby increase the internal electrical resistance of the cell. Because of this insulated layer, further hydrogen ions cannot get electrons from copper plate and get deposited in ion form. This layer of positive hydrogen ions on the copper plate exerts a repulsive force on other hydrogen ions which are approaching the copper plate. Hence current is reduced. This phenomenon is known as polarization.
First law of thermodynamics is based upon the principle of conservation of
The First Law of Thermodynamics states that heat is a form of energy, and thermodynamic processes are therefore subject to the principle of conservation of energy. This means that heat energy cannot be created or destroyed.
Laser is a device for producing
A laser is a device that emits light through a process of optical amplification based on the stimulated emission of electromagnetic radiation.
In ideal machine
If you idealize the machine by neglecting friction, then you can state an "ideal mechanical advantage".
The ideal case is represented by a machine in which the output energy is equal to the input energy. For simple geometries in which the forces are in the direction of the motion, we can characterize the ideal machine in terms of the work done as follows:
► Ideal Machine: Energy input = Energy output
The period of revolution of the earth satellite
The orbital period of a satellite depends on the mass of the planet being orbited and the distance of the satellite from the centre of the planet.
Infrasonic mechanical waves may be produced by
The infrasonic waves are produced by large vibrating bodies. These waves are not audible to a human ear. For example, infrasonic waves are produced by the vibration of the earth's surface during the earthquake.
Which part of human body is the first to be affected by nuclear radiation?
Bacteria break down the dead and decaying plant and animal matter into:
After larger particles are broken down, microorganisms further the decomposition process by secreting chemicals that digest organic material in detritus. The most prominent organisms that do this are bacteria and fungi. Bacteria and fungi that thrive in soil and feed upon dead organic matter are called saprophytes.
The Geiger-Muller detector is employed to detect:
Nuclear radiation refers to the particles and photons emitted during reactions that involve the nucleus of an atom. Examples: During the fission of U-235 the nuclear radiation that is released contains neutrons and gamma ray photons.
A Geiger counter, or a Geiger-Muller tube, is used for detecting and measuring alpha, beta and gamma radiation. It consists of a pair of electrodes with a high voltage running between them. These electrodes are surrounded by a gas, usually argon or helium. Radiation entering the tube ionizes the gas
Which instrument is used to measure the turbidity of a water sample?
Turbidity instruments are used to determine water clarity by measuring the average volume of scattered light. Turbidity can be casually defined as the observable cloudiness or haziness of a liquid which is caused by suspended solids.
The instrument used for measuring it is called nephelometer or turbidimeter, which measures the intensity of light scattered at 90 degrees as a beam of light passes through a water sample.
Which chemical process is employed to recover valuable materials from solid waste?
Pyrolysis is the thermal decomposition of materials at elevated temperatures in an inert atmosphere. It involves a change of chemical composition. The word is coined from the Greek-derived elements pyro "fire" and lysis "separating". Pyrolysis is most commonly used in the treatment of organic materials.
Nuclear radiations can cause one of the following diseases to eyes when exposed to them:
A cataract is a clouding of the lens in the eye which leads to a decrease in vision. Cataracts often develop slowly and can affect one or both eyes. Symptoms may include faded colors, blurry vision, halos around light, trouble with bright lights, and trouble seeing at night.
Cataract is caused due to the prolonged exposure of radioactive or nuclear radiations whereas retinitis and trachoma is caused due to the disorder created not by the nuclear radiation.
Which pollutant gas is released by cud-chewing domestic animals?
During a cow's digestion process, they release an approximated 75 percent of the methane gas released by animals. Cows release so much methane because of the bacteria in the cow's multiple stomachs. The bacteria allows the cows to better process their food.
Flyash is the environmental pollutant generated by
In the past, fly ash produced from coal combustion was simply entrained in flue gases and dispersed into the atmosphere. This created environmental and health concerns that prompted laws that have reduced fly ash emissions to less than 1% of ash produced.
Of the following isotopes released by a nuclear explosion, which one is of the greatest concern to human health?
External exposure to large amounts of Cs-137 can cause burns, acute radiation sickness, and even death. Exposure to Cs-137 can increase the risk for cancer because of exposure to high-energy gamma radiation.
Strontium-90 behaves like calcium in the human body and tends to deposit in bone and blood- forming tissue (bone marrow). Thus, strontium- 90 is referred to as a "bone seeker," and exposure will increase the risk for several diseases including bone cancer, cancer of the soft tissue near the bone, and leukemia.
Of the following diseases, which occurs in children less than one- year-old who have insufficient food?
Marasmus is a severe form of protein-energy malnutrition that results when a person does not consume enough protein and calories. Without these vital nutrients, energy levels become dangerously low and vital functions begin to stop.
Of the following diseases, which occurs in one-to four-year-old children from a protein-deficient diet?
Kwashiorkor, also called protein malnutrition, condition caused by severe protein deficiency. Kwashiorkor is most often encountered in developing countries in which the diet is high in starch and low in proteins. It is common in young children weaned to a diet consisting chiefly of cereal grains, cassava, plantain, and sweet potato or similar starchy foods. The condition in children was first described in 1932. The term kwashiorkor means “deposed child” (“deposed” from the mother’s breast by a newborn sibling) in one African dialect and “red boy” in another dialect. The latter term comes from the reddish orange discoloration of the hair that is characteristic of the disease. Other symptoms include dry skin and skin rash, potbelly and edema, weakness, nervous irritability, anemia, digestive disturbances such as diarrhea, and fatty infiltration of the liver.
What metal was responsible for the fatal brain disease that afflicated people eating fish caught around Minamata off the Japanese island Kyushu?
In 1956, methylmercury poisoning was discovered among the inhabitants around Minamata Bay of Shiranui Sea in Kumamoto Prefecture, Kyushu, Japan. The condition, which was caused by the ingestion of fish and shellfish that had been contaminated by methylmercury, became known as Minamata disease.
Excessive inhalation of manganese causes:
The most common health problems in workers exposed to high levels of manganese involve the nervous system. The inhalation of a large quantity of dust or fumes containing manganese may cause irritation of the lungs which could lead to pneumonia.
Of the following chemicals, tell which is a mutagen or mutation-causing agent.
Chlorinated hydrocarbons are a group of chemicals composed of carbon, chlorine, and hydrogen. As pesticides, they are also referred to by several other names, including chlorinated organics, chlorinated insecticides, and chlorinated synthetics In genetics, a mutagen is a physical or chemical agent that changes the genetic material, usually DNA, of an organism and thus increases the frequency of mutations above the natural background level.
Where did the epidemic bone-softening disease ItaiItai occur as a result of the presence of cadmium in the environment?
Cadmium poisoning can also cause softening of the bones and kidney failure. The cadmium was released into rivers by mining companies in the mountains, which were successfully sued for the damage. Itai-itai disease is known as one of the Four Big Pollution Diseases of Japan.
Which disease in children is caused by the intensive use of nitrate fertilisers?
Methemoglobinemia (MetHb) is a blood disorder in which an abnormal amount of methemoglobin is produced. Hemoglobin is the protein in red blood cells (RBCs) that carries and distributes oxygen to the body.
Which technique can map the concentration of sulphur dioxide over a whole town by operating a gadget from one location?
LIDAR is a surveying method that measures distance to a target by illuminating the target with pulsed laser light and measuring the reflected pulses with a sensor. Differences in laser return times and wavelengths can then be used to make digital 3-D representations of the target.
Which technique is employed at sea to detect and determine the position of underwater objects and also sea depth?
SONAR (originally an acronym for sound navigation ranging) is a technique that uses sound propagation (usually underwater, as in submarine navigation) to navigate, communicate with or detect objects on or under the surface of the water, such as other vessels.
Which is the standard scale employed for measuring velocities of winds?
The Beaufort scale is a scale for measuring wind speeds. It is based on observation rather than accurate measurement. It is the most widely used system to measure wind speed today. The scale was developed in 1805 by Francis Beaufort, an officer of the Royal Navy and first officially used by HMS Beagle.