Note:
(i) All questions are compulsory. The marks allotted for each question are given beside the questions.
(ii) Write your name, enrolment numbers, Al name and subject on the first page of the answer sheet.
1. Answer any one of the following questions in about 40 to 60 words.
(a) In the diagram shown alongside the displacement- position graph of a wave generated at O is shown after 0.1s. Calculate:
(i) Amplitude of the wave
(ii) Wave length
(iii) Frequency of the wave
(iv) Velocity of the wave
Answer: (a) Distance between the resting position and the maximum displacement of the wave is known as amplitude.
(b) Number of waves passing by a specific point per second is called frequency.
(c) In one time period of vibration of the particle of the medium, the distance travelled by a wave is called wavelength
(d)The distance travelled in one second by the wave is called its wave velocity.
(b) You can join resistances in different ways to obtain resistances of different values. You are given three resistances of 3 ohm each. Draw diagrams to show their different combinations. Also, calculate the equivalent resistance of each combination.
Answer: We can connect the resistances in three different combinations:
Series Combination: In this, resistors are connected one after another. The entire current path is through a single resistor, and their sum is the total resistance.
Parallel Combination: In this, all resistors are connected to a single point. The entire voltage path is through all resistors, and their reciprocal sum is the total resistance.
Mixed Combination: In this, some resistors are connected in series, and some in parallel. The total resistance is a combination of series and parallel resistances.
2. Answer any one of the following questions in about 40 to 60 words.
(a) Calculate the amount of heat required to convert 100g of ice at – 40°C into steam at 100°C
Given:
Latent heat of fusion of ice =335J/g
Latest heat of vaporization of water = 2260J/g
Specific heat capacity of ice = 2.1 J/gx C
Specific heat capacity of water = 4.2 J/gx c)
Answer:
First of all, the heat capacity of water is NOT 3200J/kg-K. It is 4186J/kg-K, or this could be rounded to 4200J/kg-K but definitely not 3200J/kg-K.
Constants that we need:
Heat capacity of water is Cpw = 4.186kJ/kg-K
Heat of vaporization of water Hw = 2257kJ/kg
Heat required to bring the water from 20C to 100C:
ΔH1 = m•Cpw•ΔT = 1.0(4.186)(80) = 334.88kJ
Heat required to vaporize the water:
ΔH2 = m•Hw = 1.0(2257) = 2257kJ
Total heat required:
334.88 + 2257 = 2591.88kJ
(b) Hydrogen and oxygen combine in the ratio of 1: 8 by mass to form water. What mass of oxygen gas would be required to react completely with 3 g of hydrogen gas?
Answer: The ratio 1:8 by mass for the combination of hydrogen and oxygen indicates that for every gram of hydrogen, 8 grams of oxygen are needed to form water. Given that you have 3 grams of hydrogen, you’ll require 3 g×8=24 g3g×8=24g of oxygen to react completely and form water.
3. Answer anyone of the following questions in about 40-60 words.
(a) Draw a labelled Diagram of a plant cell. Mention any three differences between a plant cell and an animal cell.
Answer:
|
Plant Cell |
Animal Cell |
|
Cell Wall Present |
Cell Wall Absent |
|
Large Central Vacuole |
Small Vacuoles |
|
Chloroplasts Present |
Chloroplasts Absent |
In a plant cell, the cell wall provides structure, a large central vacuole stores substances, and chloroplasts enable photosynthesis. These features are not present in animal cells.
(b) Name the causative agent and describe the mode of transmission of Malaria. What are the symptoms of this disease? List any four preventive measures for controlling spread of Malaria.
Answer: Malaria:
Causative Agent: Malaria is caused by the Plasmodium parasite.
Mode of Transmission: The primary mode of transmission is through the bite of infected female Anopheles mosquitoes.
Symptoms: Malaria symptoms include fever, chills, sweating, headache, and fatigue.
Preventive Measures:
1. Use of insecticide-treated bed nets.
2. Indoor residual spraying.
3. Antimalarial drugs for prophylaxis.
4. Elimination of mosquito breeding sites
4. Answer any one of the following questions in about 100 to 150 words.
(a) The position of a moving body at various instants of time is tabulated below:
Draw a position-time graph for the motion. What type of motion does it depict? Describe the motion giving its 3 special features in numerical terms.
Answer:
|
T (S) |
X (m) |
|
0 5 10 15 20 25 30 35 90 95 50 |
5 10 15 25 35 50 60 65 70 73 75
|
Motion Type: The position-time graph depicts irregular or non-uniform motion.
Special Features:
1. Variable Speed: The object doesn’t cover equal distances in equal intervals of time, indicating variable speed.
2. Direction Changes: The irregular pattern suggests changes in direction during motion.
3. Pauses or Stops: The flat segments show the object pausing or briefly stopping at certain times.
(b) The following diagram displays a chemical reaction. Observe carefully and answer the following questions
(i) Identify the type of chemical reaction that will take place and define it. How will the colour of the salt change?
(ii) Write the chemical equation of the reaction that takes place.
Pratyush took sulphur powder on a spatula and heated it. He collected the gas evolved by inverting a test tube over it, as shown in the figure.
Answer:
(i) Photochemical decomposition reaction will take place. Photochemical decomposition reaction is the reaction in which compound decomposes in the presence of light to form simple substances. the color of salt (i.e., silver chloride) will change from white to gray.
5. Answer any one of the following questions in about 100 to 150 words.
(a) Draw ray diagrams showing image foundation by (i) a concave lens (ii) convex lens, in case the object is placed between focus and optical centre. Describe the characteristics of the image formed in each case.
Answer: Convex Lens Reflection:
Diagram:
Description:
· In convex lens reflection, the object and its image are on opposite sides of the lens.
· The object and image are equidistant from the central axis.
Concave Lens Reflection:
Diagram:
Description:
· In concave lens reflection, the object and its image are on the same side of the lens.
· The object and image are at different distances from the central axis but on the same line.
(b) Given below are the names of some animals. Identify two animals each showing
Also Name the phylum/class of each of them; (Shark, round worm, Snake, jelly fish, tape worm, starfish)
(i) Radial symmetry
(ii) Body covered with scales
(iii) Parasitic mode of life.
Answer: (i) Radial Symmetry: Jellyfish and Starfish
1. Jellyfish:
· Phylum: Cnidaria
· Jellyfish exhibit radial symmetry, where body parts are arranged symmetrically around a central point.
2. Starfish:
· Phylum: Echinodermata
· Starfish display radial symmetry, with arms radiating from a central disk, allowing them to interact with their environment from any direction.
(ii) Body Covered with Scales: Snake and Shark
1. Snake:
· Class: Reptilia
· Snakes have scales covering their body, providing protection and aiding in movement.
2. Shark:
· Class: Chondrichthyes
· Sharks have scales known as dermal denticles, offering streamlined movement and protection.
(iii) Parasitic Mode of Life: Roundworm and Tapeworm
1. Roundworm:
· Phylum: Nematoda
· Roundworms may include parasitic species, living in various environments, including hosts.
2. Tapeworm:
· Phylum: Platyhelminthes
· Tapeworms are parasitic flatworms, adapting to a parasitic lifestyle within the digestive tracts of their hosts.
6. Prepare any one Project given below:
Answer the following:
1. A man went door-to door posing as a goldsmith. He promised to bring back the glitter of old and dull gold ornaments. An unsuspecting lady gave a set of gold bangles to him which he dipped in a particular solution. The bangles sparkled like new but their weight was reduced drastically. The lady was upset but after a futile argument the man beat a hasty repeat. Can you play the detective to find out the nature of the solution he has used?
Answer: The man likely used a solution of aqua regia, a mixture of concentrated nitric acid and hydrochloric acid. Aqua regia is known for its ability to dissolve gold, even gold that appears dull or tarnished. When the bangles were dipped in aqua regia, the acids reacted with the surface layer of gold, removing impurities and restoring the shine. However, the weight reduction suggests that the acids also dissolved some of the gold. This fraudulent practice is a form of gold adulteration, and victims often suffer financial losses due to the actual gold content being diminished.
(1) Gold is a very precious metal. Pure gold is very soft it is therefore not suitable for making jewellery. It is alloyed with either Silver or Copper to make it hard. But sometimes jewellers mix a large quantity of copper and silver in gold to earn more profit.
a) What precautions should you take while purchasing gold jewellery?
Answer: While purchasing gold jewellery, it’s essential to take the following precautions:
1. Check Purity Markings: Look for purity markings like “24K” for pure gold or “18K,” “14K,” etc. indicating the percentage of gold in the alloy.
2. Hallmark Certification: Buy from reputable jewellers who provide hallmark certification, ensuring the jewellery meets the recognized standards of purity.
3. Weighing and Pricing: Ensure the jewellery is weighed in front of you, and the price is calculated transparently based on the current market rates.
4. Ask for Details: Inquire about the alloy composition to understand the percentage of gold, silver, or copper in the jewellery.
5. Reputation of the Jeweller: Choose established and trustworthy jewellers with a good reputation to reduce the risk of fraudulent practices.
By following these precautions, one can make a more informed and secure purchase of gold jewellery.
b) Why does Government insist on purchasing Hall Marked jewellery?
Answer: Government insists on purchasing Hallmarked jewelry because:
1. Purity and Standards Guarantee: Hallmark certification ensures that the jewelry adheres to purity and quality standards.
2. Metal Accuracy: The Hallmark indicates the accurate percentage of metals used in the jewelry and specifies where each metal has been used.
3. Facilitates Informed Decision-making: In the absence of a Hallmark, buyers need to conduct more research to verify the quality and metal accuracy of their jewelry.
4. Consumer Safety: Hallmark certification assures buyers that their purchased jewelry meets predefined standards in terms of accuracy, value, and quality.
(2) Corrosion is a serious problem. Every year an enormous amount of money is spend to replace damaged iron. What steps can be taken to prevent this damage.
Answer: To prevent corrosion and extend the lifespan of iron, several steps can be taken:
Coating: Applying protective coatings like paint or zinc prevents direct exposure of iron to moisture and oxygen, reducing the chances of corrosion.
Galvanization: Coating iron with a layer of zinc through galvanization creates a sacrificial barrier, as zinc corrodes more readily than iron.
Use of Stainless Steel: Utilizing stainless steel, which contains chromium for corrosion resistance, is effective in environments prone to corrosion.
Cathodic Protection: Implementing methods like sacrificial anodes or impressed current systems helps control corrosion through electrochemical means.
Proper Drainage: Ensuring proper drainage systems prevents the accumulation of water, a key factor in corrosion.
These preventive measures collectively contribute to preserving iron structures and minimizing the economic impact of corrosion.
(3) Mercury is the only metal found in the liquid state. It is largely used in thermometers to measure the temperature. But mercury is a very dangerous metal as its density is very high. What two precautions you would take while handling the equipments containing Mercury?
Answer: Handling equipment containing mercury requires precautions due to its toxicity. Two important measures are:
1. Use Protective Gear: Always wear protective gear like gloves and safety goggles to prevent direct contact with mercury. This minimizes the risk of skin absorption or eye exposure.
2. Handle in Well-Ventilated Areas: Work in well-ventilated spaces to reduce inhalation risks. Adequate ventilation helps disperse mercury vapors, minimizing health hazards.
(a) Make two cylindrical card board formers of diameter 1 inch and 2 inch and length 6inch closely wound coils using insulated copper wire taking out of tapping’s after 50 turns, 100 turns, 250 turns on each format. Now place a magnate needle at appropriate distance.
Take first coil. Connect its 50 turns across a battery and note the deflection of magnetic needle. Repeat observations with 100 turns, 200 turns etc.
Make similar observations using the second coil.
Now insert 6 inch long iron nails inside the coil and repeat the experiment. Now answer the following questions:
1. What is the effect of increasing number of turns on the strength of the electromagnet?
Answer: Effect of Increasing Number of Turns:
· As the number of turns increases, the strength of the electromagnet also increases. This is evident from the increased deflection of the magnetic needle with a higher number of turns.
2. What is the effect of increasing the area of cross-section on the strength of the Electromagnet ?
Answer: Effect of Increasing Area of Cross-Section:
· The area of cross-section does not directly affect the strength of the electromagnet in this experiment. The strength is mainly influenced by the number of turns and the current.
3. What is the effect of using soft iron core on the strength of the electromagnet ?
Answer: Effect of Using Soft Iron Core:
· Using a soft iron core significantly enhances the strength of the electromagnet. Soft iron is easily magnetized and demagnetized, making it more effective in concentrating magnetic flux.
4. What is the effect of increasingly current on the strength of electromagnet ?
Answer: Effect of Increasing Current:
· Increasing the current flowing through the coil increases the strength of the electromagnet. This is observed in the greater deflection of the magnetic needle when higher currents are used.
5. Do the nails become magnet after some time ?
Answer: Nails Becoming Magnetized:
· Yes, the iron nails become temporary magnets when inserted inside the coil. The soft iron core inside the coil gets magnetized in the presence of the current, exhibiting magnetic properties.
These observations demonstrate key principles of electromagnetism, highlighting the factors that influence the strength of an electromagnet.