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Solved Exercise of Chapter 8 Magnetism – 9th Class Physics

January 30, 2025 by samreen

Get the complete solved exercise of Chapter 8 Magnetism from 9th Class Physics for Punjab Board students. Detailed answers, explanations, and tips to help you understand magnetism concepts

8.1 Which one of the following is not a magnetic material?

Options:
(a) Cobalt
(b) Iron
(c) Aluminium
(d) Nickel

Answer: (c) Aluminium

Explanation:
Cobalt, iron, and nickel are ferromagnetic materials, meaning they exhibit strong magnetic properties. Aluminium, on the other hand, is paramagnetic, meaning it is weakly attracted to a magnetic field but does not retain magnetism.

Tip: Remember the three main ferromagnetic elements: Iron (Fe), Cobalt (Co), and Nickel (Ni). If a metal is not one of these, it is likely non-magnetic or weakly magnetic.

8.2 Magnetic lines of force:

Options:
(a) Are always directed in a straight line
(b) Cross one another
(c) Enter into the north pole
(d) Enter into the south pole

Answer: (d) Enter into the south pole

Explanation:
Magnetic field lines emerge from the north pole and enter the south pole of a magnet. They never cross each other and follow a curved path.

Tip: Remember the rule:

Magnetic field lines always travel from north to south outside the magnet and from south to north inside the magnet.

8.3 Permanent magnets cannot be made by:

Options:
(a) Soft iron
(b) Steel
(c) Neodymium
(d) Alnico

Answer: (a) Soft iron

Explanation:
Soft iron is highly magnetically permeable but loses its magnetism quickly. Permanent magnets require materials like steel, neodymium, and alnico, which retain magnetism for a long time.

Tip: Soft iron is used in temporary magnets (e.g., electromagnets), whereas materials like steel, neodymium, and alnico are used in permanent magnets.

8.4 Permanent magnets are used in:

Options:
(a) Circuit breaker
(b) Loudspeaker
(c) Electric crane
(d) Magnetic recording

Answer: (b) Loudspeaker

Explanation:
Permanent magnets are essential in loudspeakers because they interact with an electric current to create vibrations and produce sound. Circuit breakers and electric cranes usually use electromagnets, which can be turned on or off as needed.

Tip:

Loudspeakers, microphones, and some types of electric motors use permanent magnets.
Electromagnets are used in devices where control over magnetism is needed (e.g., cranes, circuit breakers).

8.5 A common method used to magnetise a material is:

Options:
(a) Stroking
(b) Hitting
(c) Heating
(d) Placing inside a solenoid having A.C current**

Answer: (a) Stroking

Explanation:
A material can be magnetized by stroking it with a permanent magnet in one direction. Hitting or heating disrupts the alignment of magnetic domains, causing demagnetization. An A.C. current in a solenoid does not magnetize a material effectively because the alternating current reverses direction constantly.

Tip: Stroking is an easy method to remember. Another effective method is placing the material inside a solenoid carrying D.C. current.

8.6 Magnetic field direction around a bar magnet:

Answer: (d)

Explanation:
The correct diagram should show magnetic field lines exiting the north pole and entering the south pole of the bar magnet. In the given options, option (d) correctly represents this field direction.

Tip:

Field lines always go from North to South outside the magnet.
Inside the magnet, they travel from South to North.

Solutions to MCQs, Short Answer Questions, and Constructed Response Questions

Multiple-Choice Questions (MCQs)

8.7 A steel rod is magnetized by the double touch stroking method. Which one would be the correct polarity of the AB magnet?

Options:
(a) 🔴🔵🔴🔵
(b) 🔵🔴🔵🔴
(c) 🔴🔵🔵🔴
(d) 🔵🔴🔴🔵

Answer: (c) 🔴🔵🔵🔴

Explanation:
In the double-stroke method, two permanent magnets are used to stroke a steel rod from the center outward. The end where the north pole moves becomes the south pole, and the end where the south pole moves becomes the north pole. Based on this principle, option (c) is correct.

Tip:

Double-stroke method: Stroke from the center to the ends with two magnets in opposite directions.
Single-stroke method: Use one magnet to stroke in one direction.

8.8 The best material to protect a device from an external magnetic field is:

Options:
(a) Wood
(b) Plastic
(c) Steel
(d) Soft iron

Answer: (d) Soft iron

Explanation:
Soft iron has high magnetic permeability, meaning it can redirect magnetic field lines around sensitive devices, providing effective shielding.

Tip:

Soft iron is used in electromagnetic shielding to prevent interference.
Plastic and wood do not block magnetic fields effectively.

**Short Answer

Short Answer Questions

8.1 What are temporary and permanent magnets?

Answer:

Temporary Magnets: These magnets exhibit magnetism only when influenced by an external magnetic field. Example: Electromagnets.
Permanent Magnets: These retain their magnetism even after the external magnetic field is removed. Example: Neodymium magnets.

Tip:

Temporary magnets lose their magnetism easily, while permanent magnets keep it for a long time.

Keywords: Electromagnets, neodymium, retain, lose magnetism

8.2 Define the magnetic field of a magnet.

Answer:

The magnetic field is the region around a magnet where its magnetic force can be detected. It is represented by magnetic field lines that originate from the north pole and end at the south pole.

Tip:

Stronger near poles, weaker away from the magnet.

Keywords: Region, force, field lines, north to south

8.3 What are magnetic lines of force?

Answer:

Magnetic lines of force are imaginary lines that represent the direction and strength of a magnetic field. They always travel from north to south outside the magnet and south to north inside the magnet.

Tip:

Field lines never cross each other.

Keywords: Imaginary, direction, never cross, north to south

8.4 Name some uses of permanent magnets and electromagnets.

Answer:

Permanent Magnets: Used in loudspeakers, electric motors, and refrigerator doors.
Electromagnets: Used in cranes, electric bells, and MRI machines.

Tip:

Electromagnets can be turned on and off, permanent magnets cannot.

Keywords: Loudspeaker, electric motor, crane, MRI

8.5 What are magnetic domains?

Answer:

Magnetic domains are small regions inside a material where atomic magnetic moments are aligned in the same direction. When all domains align, the material becomes magnetized.

Tip:

Magnetism depends on domain alignment.

Keywords: Regions, alignment, magnetized, atomic moments

8.6 Which type of magnetic field is formed by a current-carrying long coil?

Answer:

A solenoid produces a magnetic field similar to a bar magnet, with a north and south pole.

Tip:

Right-hand rule: Curl fingers in the direction of current, thumb points to the north pole.

Keywords: Solenoid, bar magnet, right-hand rule

8.7 Differentiate between paramagnetic and diamagnetic materials.

Answer:

Paramagnetic materials: Weakly attracted to a magnetic field (e.g., aluminum, platinum).
Diamagnetic materials: Weakly repelled by a magnetic field (e.g., copper, bismuth).

Tip:

Ferromagnetic materials (like iron) are strongly attracted.

Keywords: Weakly attracted, repelled, aluminum, copper

Constructed Response Questions

8.1 Two bar magnets are stored in a wooden box. Label the poles of the magnets and identify P and Q objects.

Answer:

The poles of the bar magnets should be labeled north and south such that opposite poles face each other. The objects P and Q could be soft iron keepers used to prevent demagnetization.

Tip:

Opposite poles attract, like poles repel.
Soft iron keepers help retain magnetism.

Keywords: North, south, soft iron, demagnetization

8.2 A steel bar has to be magnetized by placing it inside a solenoid such that end A of the bar becomes N-pole and end B becomes S-pole. Draw a circuit diagram of the solenoid showing the steel bar inside it.

Answer:

To magnetize the steel bar:

Use a solenoid with a direct current (D.C.) source.
Apply the right-hand rule (curl fingers in the direction of current, thumb points to the north pole).

Tip:

A.C. current will not magnetize permanently.

Keywords: Solenoid, D.C. current, right-hand rule, magnetization

8.3 Two bar magnets are lying as shown in the figure. A compass is placed in the middle of the gap. Its needle settles in the north-south direction. Label N and S poles of the magnets. Justify your answer by drawing field lines.

Answer:

The compass aligns with the external magnetic field and points from the north pole of one magnet to the south pole of the other magnet.

Tip:

A compass always points in the direction of the magnetic field.

Keywords: Compass, north-south, field lines, alignment

Solutions to Questions

Short Answer Questions

8.4 Electric current or motion of electrons produce a magnetic field. Is the reverse process true, that is, does the magnetic field give rise to electric current? If yes, give an example and describe it briefly.

Answer:

Yes, a changing magnetic field can induce an electric current. This is explained by Faraday’s Law of Electromagnetic Induction, which states that a varying magnetic field through a coil generates an electromotive force (EMF), producing current.

Example:

Electric generators: Rotating a coil inside a magnetic field induces a current.
Transformers: A changing current in one coil induces a voltage in another coil through a magnetic field.

Tip:

Current produces a magnetic field (Oersted’s Law).
Changing magnetic fields induce current (Faraday’s Law).

Keywords: Faraday’s Law, EMF, generators, induction, transformers

8.5 Four similar solenoids are placed in a circle as shown in the figure. The magnitude of current in all of them should be the same. Show by diagram, the direction of current in each solenoid such that when current in any one solenoid is switched OFF, the net magnetic field at the center O is directed towards that solenoid. Explain your answer.

Answer:

To ensure the net magnetic field at the center (O) is directed towards the solenoid that is switched OFF:

The current directions in solenoids must be arranged symmetrically to produce equal magnetic field contributions at O.
When one solenoid is turned OFF, the balance is disturbed, making the field at O point towards the inactive solenoid.

Tip:

Use the right-hand rule: Curl fingers in the direction of current, and the thumb shows the field direction.

Keywords: Solenoid, symmetry, current, right-hand rule, field direction

Comprehensive Questions

8.1 How can you identify whether an object is a magnet or a magnetic material?

Answer:

An object is a magnet if it:

Attracts and repels another magnet (showing both attraction and repulsion).
An object is a magnetic material if it:
Only attracts a magnet but does not repel it.

Tip:

A magnet shows repulsion, magnetic materials do not.

Keywords: Attract, repel, magnet, magnetic material, test

8.2 Describe the strength of a magnetic field in terms of magnetic lines of force. Explain it by drawing a few diagrams for the fields as examples.

Answer:

The strength of a magnetic field is directly proportional to the density of magnetic field lines.
Stronger field: Closely packed lines (e.g., near poles of a magnet).
Weaker field: Widely spaced lines (e.g., far from the magnet).

Tip:

Dense lines = strong field, sparse lines = weak field.

Keywords: Field strength, density, magnetic lines, poles

8.3 What is a circuit breaker? Describe its working with the help of a diagram.

Answer:

A circuit breaker is a safety device that automatically stops current flow when there is an overload or short circuit.

It uses an electromagnet to detect excessive current.
When current exceeds a safe limit, the electromagnet pulls the switch, breaking the circuit.

Tip:

Used in homes, industries, and power plants for safety.

Keywords: Circuit breaker, safety, electromagnet, overload, short circuit

8.4 A magnet attracts only a magnet. Explain the statement.

Answer:

This statement is incorrect because:

A magnet attracts both magnetic materials (e.g., iron) and other magnets.
However, only another magnet can repel it, which confirms that an object is truly a magnet.

Tip:

Attraction does not confirm magnetism; repulsion does.

Keywords: Attraction, repulsion, test, magnetic material

8.5 Differentiate between paramagnetic, diamagnetic, and ferromagnetic materials with reference to the domain theory.

Answer:

Property	Paramagnetic	Diamagnetic	Ferromagnetic
Behavior in field	Weakly attracted	Weakly repelled	Strongly attracted
Magnetic domains	Random, slightly align	Oppose the field	Strongly aligned
Examples	Aluminum, platinum	Copper, gold	Iron, cobalt, nickel

Tip:

Ferromagnetic materials have strong, aligned domains.

Keywords: Domains, alignment, attraction, repulsion, iron, copper

8.6 Why are ferromagnetic materials suitable for making magnets?

Answer:

Ferromagnetic materials (e.g., iron, cobalt, nickel) are suitable because:

Their magnetic domains remain aligned after magnetization.
They have high permeability (easily magnetized).
They retain magnetism for a long time.

Tip:

Strong, aligned domains = strong permanent magnet.

Keywords: Ferromagnetic, domains, alignment, retain magnetism

Solved Exercise of Chapter 5: Turning Effect of Force | Physics Class 9th

January 21, 2025 by samreen

Get the solved exercise of Chapter 5, Turning Effect of Force, for Physics Class 9th based on the new syllabus. Tailored for Punjab Board and Lahore Board students, this comprehensive guide will help you ace your exams.

4.1

Statement: A particle is simultaneously acted upon by two forces of 4 and 3 newtons. The net force on the particle is:
Options:
(a) 1 N
(b) Between 1 N and 7 N
(c) 5 N
(d) 7 N
Answer: (c) 5 N
Explanation: The net force is calculated using the Pythagorean theorem since the forces are perpendicular: Fnet=√42+32=√16+9=√25=5

Tips and Tricks: Use the Pythagorean theorem for forces acting at right angles. The formula is Fnet=√F₁²+F₂²

4.2

Statement: A force FF is making an angle of 60^∘ with the x-axis. Its y-component is equal to:
Options:
(a) F
(b) Fsin⁡60^∘
(c) Fcos⁡60^∘
(d) Ftan⁡60^∘
Answer: (b) Fsin⁡60^∘
Explanation: The y-component of a force is calculated as F_y=Fsin⁡θ. Substituting θ=60^∘, the y-component becomes Fsin⁡60^∘F .
Tips and Tricks: Memorize the formulas for components of force:

F_x=Fcos⁡θ
F_y=Fsin⁡θ

4.3

Statement: Moment of force is called:
Options:
(a) Moment arm
(b) Couple
(c) Couple arm
(d) Torque
Answer: (d) Torque
Explanation: The moment of force about a point is known as torque, which is the product of force and perpendicular distance. Formula: τ=F×r
Tips and Tricks: Torque is also referred to as the rotational equivalent of force.

4.4

Statement: If F and r are the forces acting on a body and τ is the torque produced in it, the body will be completely in equilibrium under:
Options:
(a) ΣF=0 and Στ= 0
(b) ΣF=0 or Στ= 0
(c) ΣF≠0 and Στ= 0
(d) ΣF=0 and Στ≠0
Answer: (a) ΣF=0 and Στ= 0
Explanation: For a body to be in equilibrium, both the net force and the net torque acting on it must be zero.
Tips and Tricks: Equilibrium conditions:

Translational equilibrium: ΣF= 0
Rotational equilibrium: Στ = 0.

4.5

Statement: A shopkeeper sells his articles by a balance having unequal arms of the pans. If he puts the weights in the pan having a shorter arm, then the customer:
Options:
(a) Loses
(b) Gains
(c) Neither loses nor gains
(d) Not certain
Answer: (a) Loses
Explanation: When weights are placed on the shorter arm, the force produced is smaller, leading to an imbalance that favors the shopkeeper.
Tips and Tricks: Analyze the torque balance when arms are unequal: τ=F×r.

4.6

Statement: A man walks on a tight rope. He balances himself by holding a bamboo stick horizontally. It is an application of:
Options:
(a) Law of conservation of momentum
(b) Newton’s second law of motion
(c) Principle of moments
(d) Newton’s third law of motion
Answer: (c) Principle of moments
Explanation: The man uses the bamboo stick to shift his center of gravity and balance the moments on either side of the rope.
Tips and Tricks: Recall that balancing requires the moments about a pivot to be equal.

4.7

Statement: In the stable equilibrium, the center of gravity of the body lies:
Options:
(a) At the highest position
(b) At the lowest position
(c) At any position
(d) Outside the body
Answer: (b) At the lowest position
Explanation: In stable equilibrium, the body’s center of gravity is at the lowest point to maintain maximum stability.
Tips and Tricks: Stability depends on the position of the center of gravity: lower is more stable.

4.8

Statement: The center of mass of a body:
Options:
(a) Lies always inside the body
(b) Lies always outside the body
(c) Lies always on the surface of the body
(d) May lie within, outside, or on the surface
Answer: (d) May lie within, outside, or on the surface
Explanation: The center of mass depends on the distribution of mass. For example:

A uniform solid has its center of mass within the body.
A hollow sphere can have its center of mass outside the material body.
Tips and Tricks: Think about examples like rings or irregularly shaped bodies to determine the center of mass.

4.9

Statement: A cylinder resting on its circular base is in:
Options:
(a) Stable equilibrium
(b) Unstable equilibrium
(c) Neutral equilibrium
(d) None of these
Answer: (a) Stable equilibrium
Explanation: When the cylinder is slightly disturbed, it will return to its original position because its center of gravity remains low and stable.
Tips and Tricks: Objects with a broad base and low center of gravity are usually in stable equilibrium.

4.10

Statement: Centripetal force is given by:
Options:
(a) rF
(b) rFcos⁡θ
(c) mv²/r
(d) mv/r
Answer: (c) mv²/r
Explanation: Centripetal force is the force required to keep an object moving in a circular path, given by the formula: Fc=mv²/r

where mm is the mass, vv is the velocity, and rr is the radius of the circular path.
Tips and Tricks: Memorize the formula for centripetal force. It directly depends on the mass and velocity squared and inversely on the radius.

Short Answer Questions

4.1 Define like and unlike parallel forces.
Answer:

Like parallel forces: Forces acting in the same direction along parallel lines.
Unlike parallel forces: Forces acting in opposite directions along parallel lines.

4.2 What are rectangular components of a vector and their values?
Answer:
Rectangular components of a vector are the projections of the vector along mutually perpendicular axes (usually x and y).

Vx=Vcos⁡θ
Vy=Vsin⁡θ

4.3 What is the line of action of a force?
Answer:
The line of action of a force is an imaginary line that extends along the direction of the force. It determines the point of application and the torque produced by the force.

4.4 Define moment of force. Prove that τ=Fsin⁡θ, where θ\theta is the angle between r and F.
Answer:

Definition: The moment of a force (or torque) is the measure of its ability to rotate an object about an axis or a point.
Proof:
Torque (τ\tau) is given by the formula:

τ=r×F=rFsin⁡θ

where r is the perpendicular distance from the axis of rotation, F is the applied force, and θ is the angle between r and F.

4.5 With the help of a diagram, show that the resultant force is zero but the resultant torque is not zero.
Answer:
Draw a diagram where two equal and opposite forces are acting on a body (e.g., a rectangular body). The forces cancel each other out, resulting in ΣF=0. However, since these forces do not share the same line of action, they produce a couple, resulting in τ≠0.

4.6 Identify the state of equilibrium in the given figure.
Answer:
(a) Stable equilibrium (the cone on its base)
(b) Neutral equilibrium (sphere on a flat surface)
(c) Unstable equilibrium (cylinder on its curved surface).

Constructed Response Questions

4.1 A car travels at the same speed around two curves with different radii. For which radius does the car experience more centripetal force? Prove your answer.
Answer:

Formula: Centripetal force Fc=mv²/r
When v (velocity) and m (mass) are constant, Fc is inversely proportional to rr.
For the smaller radius, Fc is larger because r is smaller.
Proof: Assume two radii r1<r2r_1 < r_2, then:

Fc₁=mv²/r1>Fc₂=mv²/r₂

4.2 A ripe mango does not normally fall from the tree. But when the branch of the tree is shaken, the mango falls down easily. Can you tell the reason?
Answer:
The mango remains stationary due to inertia. When the branch is shaken, the inertia of the mango resists the motion of the branch, causing the mango to lose its support and fall due to gravity.

4.3 Discuss the concepts of stability and center of gravity in the context of objects toppling over. Provide an example where an object’s center of gravity affects its stability.
Answer:

Stability: An object is stable if its center of gravity lies within its base of support.
Toppling: If the line of action of weight (passing through the center of gravity) falls outside the base of support, the object topples.
Example: A tall, narrow vase is less stable compared to a wide, flat vase because its center of gravity is higher and more likely to shift outside the base.

Short Questions

4.4 Why an accelerated body cannot be considered in equilibrium?
Answer:
An accelerated body is not in equilibrium because:

In equilibrium, the net force (ΣF) and net torque (Στ) acting on the body must be zero.
An accelerated body has a non-zero net force (F=ma), which violates the equilibrium condition.

4.5 Two boxes of the same weight but different heights are lying on the floor of a truck. If the truck makes a sudden stop, which box is more likely to tumble over? Why?
Answer:
The taller box is more likely to tumble over because it has a higher center of gravity.

When the truck stops suddenly, inertia causes the box to tilt.
A higher center of gravity increases the chance of the line of action of weight moving outside the base of support, leading to toppling.

Comprehensive Questions

4.1 Explain the principle of moments with an example.
Answer:

Principle of Moments: For a body to be in rotational equilibrium, the sum of clockwise moments must equal the sum of anticlockwise moments about a pivot point:

ΣClockwise moments=ΣAnticlockwise moments

Example: A seesaw in balance:
- If a child of weight W1 sits at a distance d1d_1 from the pivot on one side, and another child of weight W2 sits at d2 on the other side, equilibrium is achieved when:

W1×d1=W2×d2

4.2 Describe how you could determine the center of gravity of an irregular-shaped lamina experimentally.
Answer:

Suspend the irregular lamina freely from one point.
Use a plumb line to draw a vertical line along the lamina from the suspension point.
Suspend the lamina from another point and repeat the process.
The intersection of the lines is the center of gravity.

4.3 State and explain two conditions of equilibrium.
Answer:

Translational Equilibrium:
The net force acting on the body is zero (ΣF=0).
- Example: A book resting on a table where gravitational force is balanced by the normal force.
Rotational Equilibrium:
The net torque acting on the body is zero (Στ=0).
- Example: A balanced beam on a fulcrum where clockwise and anticlockwise torques are equal.

4.4 How the stability of an object can be improved? Give a few examples to support your answer.
Answer:
Ways to Improve Stability:

Lower the center of gravity: The closer the center of gravity is to the base, the more stable the object.
- Example: Racing cars have low centers of gravity for stability at high speeds.
Widen the base of support: A broader base increases stability by making it harder for the center of gravity to shift outside the base.
- Example: Tripods have wide bases to prevent tipping.
Add weight near the base: Heavier bases prevent toppling.
- Example: Tall structures like towers have heavy foundations.
Align weight along the base: Ensure the line of action of weight remains within the base of support.
- Example: A gymnast balances carefully to maintain stability.

Let me know if further explanations are needed!

The science of biology-9th class solved Exercise

January 10, 2025 by samreen

Biology 9th is a foundational subject under the Lahore Board and Punjab Board syllabus. The science of biology explores the study of life, organisms, and their interactions, helping students build essential knowledge for higher studies in medicine, agriculture, and environmental sciences.

1. Which branch of Biology focuses on the study of the structure and function of cells?

Options:
a) Cytology
b) Microbiology
c) Histology
d) Ecology
Answer: a) Cytology
Tip/Trick: The prefix “cyto-” means “cell,” so Cytology is the study of cells.

2. The study of the processes of heredity and variation in living organisms is known as:

Options:
a) Ecology
b) Genetics
c) Anatomy
d) Proteomics
Answer: b) Genetics
Tip/Trick: Genetics deals with genes and inheritance, which govern heredity and variation.

3. Insulin made through bacteria is an example of the technique of:

Options:
a) Parasitology
b) Biotechnology
c) Biochemistry
d) Histology
Answer: b) Biotechnology
Tip/Trick: Biotechnology involves using organisms or biological processes to create useful products like insulin.

4. Heart pumps, the brain memorizes, kidneys excrete. The statement comes from:

Options:
a) Physiology
b) Anatomy
c) Morphology
d) Cardiology
Answer: a) Physiology
Tip/Trick: Physiology focuses on the functions and processes of living organisms and their parts.

5. Which branch of Biology involves the study of the classification of organisms?

Options:
a) Taxonomy
b) Physiology
c) Palaeontology
d) Biogeography
Answer: a) Taxonomy
Tip/Trick: Taxonomy is about naming, classifying, and organizing organisms into groups.

6. Which step comes between making a hypothesis and doing experiments?

Options:
a) Making deductions
b) Making observations
c) Summarizing results
d) Analyzing data
Answer: b) Making observations
Tip/Trick: Observations help refine hypotheses and guide experimental design.

7. Which of the following is NOT a characteristic of the scientific method?

Options:
a) It relies on evidence
b) It involves formulating hypotheses
c) Hypotheses will always be correct
d) It requires rigorous testing
Answer: c) Hypotheses will always be correct
Explanation: Hypotheses are tentative explanations and can be disproven.
Tip/Trick: Remember that in science, hypotheses are tested and may be rejected or refined.

8. Choose the correct sequence of steps of the scientific method.

Options:
a) Observations → hypothesis → deduction → experiments
b) Observations → hypothesis → law → theory
c) Hypothesis → observations → deduction → experiments
d) Law → theory → deduction → observations
Answer: a) Observations → hypothesis → deduction → experiments
Explanation: The scientific method begins with observations, followed by forming a hypothesis, making deductions, and performing experiments.
Tip/Trick: Think of it as “observe first, then hypothesize, test, and conclude.”

9. People who slept near smoky fire had less chance to suffer from malaria. Why?

Options:
a) Smoke kills Plasmodium in their blood
b) Fire increases temperature and Plasmodium are killed in air
c) Mosquitoes cannot tolerate smoke and are repelled
d) Smoke kills Plasmodium present in mosquitoes
Answer: c) Mosquitoes cannot tolerate smoke and are repelled
Explanation: Smoke repels mosquitoes, reducing their bites and preventing the spread of malaria.
Tip/Trick: Remember that mosquitoes are the carriers of malaria, and repelling them is effective.

10. Experiments are very important in the scientific method because a researcher:

Options:
a) Always gets correct results
b) Disproves many hypotheses and gets some hypotheses proved
c) Is sure that he will prove the hypotheses
d) Gets a chance to work in the laboratory
Answer: b) Disproves many hypotheses and gets some hypotheses proved
Explanation: Experiments validate or refute hypotheses, advancing scientific understanding.
Tip/Trick: Science progresses by eliminating incorrect hypotheses and validating correct ones.

Short Questions

1. Define the following branches of Biology:

Genetics: The study of heredity and the variation of inherited traits.
Anatomy: The study of the structure of organisms and their parts.
Palaeontology: The study of fossils to understand past life and evolution.
Marine Biology: The study of organisms in the ocean and other saltwater environments.
Pathology: The study of diseases, their causes, and effects.

2. Which branch of Biology involves the study of the development and growth of organisms from fertilization to adulthood?

Answer: Embryology.
Explanation: Embryology focuses on the development of organisms from a single cell to maturity.

3. How is the profession of medicine and surgery different from animal husbandry?

Answer: Medicine and surgery deal with diagnosing and treating human diseases, while animal husbandry involves breeding, feeding, and caring for animals for agricultural purposes.

4. Differentiate between Morphology and Physiology.

Answer:
- Morphology: The study of the structure, shape, and form of organisms.
- Physiology: The study of the functions and processes of living organisms.

5. What is Computational Biology?

Answer: Computational Biology is the application of data analysis, mathematical models, and algorithms to study biological systems.

6. What is the role of observation and experimentation in the scientific method?

Answer: Observation helps identify patterns and formulate hypotheses, while experimentation tests these hypotheses to validate or refute them.

Detailed Answers for Section C

1. Link the study of Biology with that of Physics, Chemistry, Statistics, Geography, Economics, and Computer Science.

Biology is interconnected with many disciplines:
- Physics: Explains biological phenomena like fluid dynamics in blood flow and biomechanics in movement.
- Chemistry: Essential for understanding biochemical reactions like photosynthesis, respiration, and digestion.
- Statistics: Helps in analyzing experimental data, such as population genetics or epidemiological studies.
- Geography: Influences ecosystems, biodiversity, and environmental studies.
- Economics: Impacts resource management, agricultural biology, and biotechnology industries.
- Computer Science: Supports bioinformatics, genetic sequencing, and computational biology for data analysis and modeling.

2. Explain how the study of Biology can lead to different professional studies.

Biology serves as a foundation for numerous professions:
- Medicine and Surgery: Diagnosis and treatment of diseases.
- Agriculture and Horticulture: Crop production and pest management.
- Environmental Science: Ecosystem conservation and pollution control.
- Biotechnology: Development of medicines, vaccines, and genetically modified crops.
- Pharmaceuticals: Drug design and clinical research.
- Research: Advancing knowledge in genetics, microbiology, and molecular biology.

3. Science is a collaborative field in which scientists work together to share knowledge. Prove this statement by giving examples.

Collaboration is vital for scientific progress:
- Human Genome Project: Involved scientists from various countries to map all human genes.
- COVID-19 Vaccine Development: Teams across the globe shared data to develop effective vaccines quickly.
- Discovery of DNA Structure: James Watson, Francis Crick, Rosalind Franklin, and Maurice Wilkins worked together to elucidate DNA’s double helix.
- Climate Change Research: Requires collaboration between biologists, geographers, and meteorologists.

4. How is a hypothesis converted to theory, law, and principle?

Hypothesis: A testable statement based on observations.
- Example: “Plants grow faster with more sunlight.”
Theory: When a hypothesis is repeatedly tested and supported by evidence.
- Example: The Theory of Evolution explains biodiversity through natural selection.
Law: A universal statement that describes a consistent natural phenomenon.
- Example: Mendel’s Laws of Inheritance explain genetic traits.
Principle: A fundamental truth that serves as a basis for other scientific concepts.
- Example: The Principle of Homeostasis explains the stability of internal environments.

5. What are the basic steps a scientist adopts in order to solve scientific problems?

Steps in the Scientific Method:
1. Observation: Identify a phenomenon or problem.
2. Hypothesis: Propose a possible explanation.
3. Experimentation: Design and conduct tests to validate the hypothesis.
4. Data Analysis: Interpret experimental results.
5. Conclusion: Accept, reject, or refine the hypothesis.
6. Publication: Share findings for peer review.

6. Describe the work of different scientists in discovering the cause of malaria.

Charles Laveran: First observed the malaria parasite in a patient’s blood in 1880.
Patrick Manson: Demonstrated the transmission of parasites through mosquitoes.
Ronald Ross: Proved that the Anopheles mosquito is the vector for malaria by showing parasites in the mosquito’s stomach.
Giovanni Battista Grassi: Confirmed Ross’s findings and identified the lifecycle of the parasite.

7. Write a descriptive note on the experiments performed by Ross.

Ronald Ross’s experiments:
1. In 1897, Ross dissected mosquitoes fed on malaria-infected patients and found Plasmodium parasites in their stomachs.
2. He demonstrated the lifecycle of Plasmodium in mosquitoes, showing that mosquitoes were the vector for malaria.
3. His experiments took place in India, where he meticulously studied mosquito behavior and malaria transmission.
4. His work earned him the Nobel Prize in 1902, revolutionizing the understanding and prevention of malaria.