WBBSE Solutions For Class 8 School Science Chapter 5 Analysis Of Natural Phenomena Short Answer Type Questions

Chapter 5 Analysis Of Natural Phenomena Short Answer Type Questions

 

Question 1. Write short notes on the lightning conductors.
Answer:

Lightning Conductors

To protect the house and the electrical appliances inside the house from lightning, a lightning conductor is used. This is a metallic rod (usually copper, a conductor of electricity) mounted vertically at the top of a building.

The top of the rod has some small skewers. A wide-based metal plate is buried at least 5 to 6 feet below the ground. A thick copper strip (or wire made up of any good conductor material) is connected between the rod at the top of the building and the metal plate buried deep inside the ground.

If the lighting strip is, the current easily passes through the strip or wire to the ground. Consequently, no substantial damage occurs to the building as the electrical energy associated with the lightning does not pass through the building.

If a building (or any tall structure) is not protected by the lightning conductor, then the tremendous electrical energy produced by lightning would pass through the walls of the building causing damage to the materials of the wall and thus making the wall unsafe. It can even set the building on fire.

A lightning conductor protects a building against lightning by providing its electric energy with an easy path to be discharged to the ground.

WBBSE Solutions For class 8 Chapter 4 Analysis of natural phenomena lighting conductors

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Question 2. Discuss the do’s and don’t when someone is inside a house during a thunderstorm.
Answer:

The Do’s And Don’t When Someone Is Inside A House During A Thunderstorm

When one is inside a house during a thunderstorm, the doors and windows of the house should be properly shut and one must not stand or sit near them.

During thunderstorms and lightning, it is better to stay away from metal pipes and electrical wires. Land phones should not be used.

Mobile phones are relatively safe, but it is better not to use them since the other person to whom one is talking might be using land phones.

Household electrical appliances such as television, refrigerator, toasters, microwave oven etc. should be switched off and unplugged. The use of running water coming, through a pipe should be avoided.

Question 3. What do you mean by the epidemic and pandemic diseases?
Answer:

Epidemic And Pandemic Diseases:

An epidemic may be restricted to one location; however, if it spreads to other countries or continents and affects a substantial number of people, it may be termed a pandemic.

The declaration of an epidemic usually requires a good understanding of a baseline rate of incidence; epidemics for certain diseases, such as influenza, are defined as reaching some defined increase in incidence above this baseline.

Question 4. What is the horizontal and vertical transmission of diseases?
Answer:

The horizontal and vertical transmission of diseases:

Horizontal transmission: Lateral spread to others in the same group and at the same time; spread to contemporaries.

Vertical transmission: From one generation to the next, perhaps transovarially or by intrauterine infection of the foetus. Some retroviruses are transmitted in the germ line, i.e. their genetic material is integrated into the DNA of either the ovum or sperm.

Question 5. What is meant by point source or single exposure epidemics?
Answer:

Point source or single exposure epidemics:

In this type of epidemic the disease agent responsible for the spread of the disease is exposed to a susceptible population at one point in time and only once.

A very good example of this type of epidemic is the occurrence of food poisoning due to the consumption of contaminated food at a feast. In this type of epidemic, there is a sudden rise in cases, which declines equally fast.

Question 6. Write briefly about cholera.
Answer:

Cholera:

Cholera is an acute intestinal infection caused by ingestion of food or water contaminated with the bacterium Vibrio cholera. It has a short incubation period and produces an enterotoxin that causes a copious, painless, watery diarrhoea that can quickly lead to severe dehydration and death if treatment is not promptly given. Vomiting also occurs in most patients.

Question 7. What are the symptoms of dengue?
Answer:

Symptoms of dengue:

Dengue is characterized by fever with a headache, joint pain, rash, low platelet, bleeding and breathing difficulty.

Question 8. What are the types of hepatitis?
Answer:

Types of hepatitis:

There are five main hepatitis viruses, referred to as types A, B, C, D and E. In particular, types B and C lead to chronic disease in hundreds of millions of people and together, are the most common causes of liver cirrhosis and cancer.

Question 9. What are the types of epidemics? Name them.
Answer:

Types of epidemics:

WBBSE Solutions For class 8 Chapter 4 Analysis of natural phenomena epidemic flow chart

Question 10. Name a few precautions to be taken at school to reduce the incidence of infectious diseases.
Answer:

Few Precautions To Be Taken At School To Reduce The Incidence Of Infectious Diseases:

  1. Well-aerated and cross-ventilated classroom.
  2. Physical distancing
  3. Provision of clear water, soap and sanitization facilities
  4. Regular and proper immunization of students.

 

 

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