Question Discussion & Solution

The correct answer is option 4) i.e. ∞

CONCEPT:

• ​The time period of a pendulum is given by the equation:

​\(\Rightarrow T = 2\pi\sqrt{\frac {L}{g}}\)

Where L is the length of the string of pendulum and g is the acceleration due to gravity.

EXPLANATION:

• At a height of 900 km from the earth's surface gravity is absent.

Therefore, g = 0.

Substituting g = 0,

\(\Rightarrow T = 2\pi\sqrt{\frac {L}{0}} = ∞\)

Thus, the time period of the pendulum at a distance of 900 km from the Earth will be infinite.

The correct answer is ​Wide Area Network (WAN).

Key Points

• A global system of interconnected computers, using a standardized Internet Protocol suite for communication and sharing information is called the Internet.
• World Wide Web or ‘www’ is a collection of web pages that can easily be published on the Internet and read by millions of its users. 
• The first development was the introduction of host-to-host network interactions.
• This was first observed in ARPANET in 1969.
• It was developed by the Advanced Research Projects Agency (APRA) of the Department of Defence, U.S. It was one of the first general usages of computer networks.

Important Points

• A personal area network, or PAN, is a computer network organized around an individual person within a single building. This could be inside a small office or residence.
• A typical PAN would include one or more computers, telephones, peripheral devices, video game consoles, and other personal entertainment devices.
• A local area network, or LAN, consists of a computer network at a single site, typically an individual office building. A LAN is very useful for sharing resources, such as data storage and printers.
• LANs can be built with relatively inexpensive hardware, such as hubs, network adapters, and Ethernet cables.
• A metropolitan area network, or MAN, consists of a computer network across an entire city, college campus, or small region. A MAN is larger than a LAN, which is typically limited to a single building or site.
• Depending on the configuration, this type of network can cover an area from several miles to tens of miles. A MAN is often used to connect several LANs together to form a bigger network.
• When this type of network is specifically designed for a college campus, it is sometimes referred to as a campus area network, or CAN.
• A wide area network, or WAN, occupies a very large area, such as an entire country or the entire world. A WAN can contain multiple smaller networks, such as LANs or MANs. The Internet is the best-known example of a public WAN. 

The correct answer is CPU.

Key Points

• CPU (Central Processing Unit) -
  • It is the main part of the computer, it can also be called the 'brain of the computer'.
  • Its function is to process the inputs and instructions coming on the computer. 
  • This unit of computer performs arithmetic, logical, control functions, input functions, and output functions. 
  • It is also commonly known as a processor.

Additional Information

• Motherboard -
  • It is a printed circuit board installed in most electronic plants such as laptops, computers, etc.
  • It is also called the mainboard or system board.
  • The main part of the motherboard is its chipset.
• RAM (Random Access Memory) -
  • This is a type of memory, we also know it by the name of Primary Memory.
  • There are two types of RAM. Static RAM and Dynamic RAM

The correct answer is Soap solution is alkaline.

Concept:

• Indicators are the substances that are used to identify whether the given substance is an acid or a base.
• There are two types of indicators:
  • Natural: These indicators are obtained from natural sources like plants. 
  • Turmeric, litmus, china rose petals, etc., are some of the naturally occurring indicators.
  • The most commonly used natural indicator is litmus.
  • It is extracted from lichens.
  • It is available in the form of a solution, or in the form of strips of paper, known as litmus paper.
  • Generally, it is available as red and blue litmus paper.
  • Man-made: Phenolphthalein, Methyl orange are some of the man-made indicators.

Explanation:

• • The indicators change their colour when added to a solution containing an acidic or a basic substance.
  • Turmeric is a natural indicator. It contains the substance

curcumin which changes colour with pH.

• When a substance is basic, the colour is red, whereas when the substance is acidic, the colour of turmeric turns yellow to brown

• Turmeric stains on the shirt turn red when washed with soap because the soap solution is basic in nature which changes the yellow colour of Turmeric into red colour.
• It is because turmeric contains tartaric acid, while the soap contains a sodium hydroxide base. When an acid reacts with a base, a neutralization reaction takes place and the stain becomes neutral.

Neutralization Reaction

• A neutralization reaction can be defined as a chemical reaction in which an acid and base quantitatively react together to form salt and water as products.

Saponification

• Saponification is the hydrolysis of an ester with NaOH or KOH to give alcohol and sodium or potassium salt of the acid.

The correct answer is Barium.

Key Points

• Metal salts commonly used in firework displays include calcium chloride, sodium nitrate, barium chloride, copper chloride, etc.
• The green flame produced in fireworks is due to the presence of Barium.
• The blue flame is due to the presence of Copper.
• The orange flame is due to the presence of Calcium.
• A yellow flame is due to the presence of Sodium.
• Lithium is used to impart a red colour to fireworks.

Additional Information

• Barium (Ba):
  • The atomic number is 56.
  • It is mostly used in drilling fluids for oil and gas wells and also used in paints and glassmaking.
  • It is found in combination with other elements.
  • Barite is one of the major ores of Barium.
• Calcium (Ca):
  • The atomic number is 20.
  • Calcium provides strength to bones and teeth along with vitamins.
  • It also plays an important role in blood formation, muscle contraction, clotting of blood, etc.
  • Milk, eggs, fish, etc. are the main sources of calcium.
• Lithium (Li):
  • Atomic Number is 3.
  • Lithium is the lightest metal on the periodic table.
  • It is widely used in rechargeable batteries for mobile phones, laptops, digital cameras, etc.
• Chromium (Cr):
  • The atomic number is 24.
  • It is used in manufacturing stainless steel.
  • Chromite is the major ore of Chromium.
  • It is a blue-white hard, brittle, and very corrosion-resistant metal and is used to produce several alloys.