Students must start practicing the questions from CBSE Sample Papers for Class 10 Science with Solutions Set 1 are designed as per the revised syllabus.
CBSE Sample Papers for Class 10 Science Set 1 with Solutions
Time: 3 Hours
Maximum Marks: 80
Instructions
- This question paper consists of 39 questions in 5 sections.
- All questions are compulsory. However, an internal choice is provided in some questions. A student is expected to attempt only one of these questions.
- Section A consists of 20 objective-type questions carrying 1 mark each.
- Section B consists of 6 Very Short questions carrying 2 marks each. Answers to these questions should be in the range of 30 to 50 words.
- Section C consists of 7 Short Answer questions with 3 marks each. Answers to these questions should be in the range of 50 to 80 words.
- Section D consists of 3 Long Answer questions with 5 marks each. Answers to these questions should be in the range of 80 to 120 words.
- Section E consists of 3 source-based/case-based units of assessment of 4 marks each with sub-parts.
Section A
Select and write the most appropriate option out of the four options given for each of the questions 1-20.
Question 1.
Identify the product that represents the solid state in the above reaction.
(a) Barium chloride
(b) Barium sulphate
(c) Sodium chloride
(d) Sodium sulphate
Answer:
(b) Barium sulphate
The reaction involved is as follows.
Question 2.
The colour of the solution observed after 30 min of placing zinc metal in copper sulphate solution is
(a) blue
(b) colourless
(c) dirty green
(d) reddish brown
Answer:
(b) colourless
Zinc being more reactive than copper displaces it from copper sulphate solution and forms a colourless solution of zinc sulphate.
Question 3.
Mild non-corrosive basic salt is
(a) Ca(OH)2
(b) NaCl
(c) NaOH
(d) NaHCO3
Answer:
(d) NaHCO3
Among the given options, mild to non-corrosive basic salt is NaHCO3.
Question 4.
On adding dilute sulphuric acid to a test tube containing a metal X, a colourless gas is produced when a burning match stick is brought near it. Which of the following correctly represents metal X?
(a) Sodium
(b) Zinc
(c) Copper
(d) Silver
Answer:
(a) Sodium
The metal X is sodium as on reacting with dilute H2SO4 it releases hydrogen gas which burns when a match stick is brought near to it. Note Zinc also reacts with dil.H2SO4 to give H2 gas but at a slower rate as compared to Na.
Question 5.
Which one of the following correctly represents sodium oxide?
Answer:
Among the given options, the correct representation of sodium oxide is given as
Question 6.
An element with atomic number _______ will form a basic oxide.
(a) 7 (2, 5)
(b) 17 (2, 8, 7)
(c) 14 (2, 8, 4)
(d) 11 (2, 8, 1)
Answer:
(d) 11 (2, 8, 1)
The oxides of metal are basic. Thus, among the given options, an element with atomic number 11 will form a basic oxide.
Question 7.
An element M has 50% of the electrons filled in the 3rd shell as in the 2nd shell. The atomic number of M is
(a) 10
(b) 12
(c) 14
(d) 18
Answer:
(c) The electronic configuration of an element with atomic number 14 is
K L M
2 8 4
Thus, it contains 4 electrons in the M shell, i.e. 3rd shell which is 50% of the electrons that are present in the 2nd shell (i.e. 8 electrons)
Question 8.
Generally, food is broken and absorbed within the body of organisms. In which of the following organisms, is it done outside the body?
(a) Amoeba
(b) Mushroom
(c) Paramecium
(d) Lice
Answer:
(b) Mushroom
Question 9.
Receptors are usually located in sense organs. Gustatory receptors are present in
(a) tongue
(b) nose
(c) eye
(d) ear
Answer:
(a) tongue
Question 10.
A farmer wants to grow banana plants genetically similar enough to the plants already available in his field. Which one of the following methods would you suggest for this purpose?
(a) Regeneration
(b) Budding
(c) Vegetative propagation
(d) Sexual reproduction
Answer:
(c) Vegetative propagation
Question 11.
The height of a plant is regulated by
(a) DNA which is directly influenced by the growth hormone
(b) Genes which regulate the proteins directly
(c) Growth hormones under the influence of the enzymes coded by a gene
(d) Growth hormones directly under the influence of a gene
Answer:
(c) Growth hormones under the influence of the enzymes coded by a gene
Question 12.
A sportsman, after a long break from his routine exercise, suffered muscular cramps during a heavy exercise session. This happened due to
(a) lack of carbon dioxide and formation of pyruvate
(b) presence of oxygen and formation of ethanol
(c) lack of oxygen and formation of lactic acid
(d) lack of oxygen and formation of carbon dioxide
Answer:
(c) lack of oxygen and formation of lactic acid
Question 13.
An object is placed in front of a convex mirror. Its image is formed
(a) at a distance equal to the object distance in front of the mirror
(b) at twice the distance of the object in front of the mirror
(c) half the distance of the object in front of the mirror
(d) behind the mirror and its position varies according to the object’s distance
Answer:
(d) The image is formed behind the mirror and its position varies according to the object’s distance.
Question 14.
When light enters the atmosphere, it strikes extremely fine particles, which deflect the rays of light in all possible directions. This is due to
(a) reflection of light
(b) atmospheric refraction
(c) scattering of light
(d) dispersion of light
Answer:
(c) scattering of light
This phenomenon is due to the scattering of light.
Question 15.
In 1987, an agreement was formulated by the United Nations Environment Programme (UNEP) to freeze the production of X to prevent depletion of Y. X and Y respectively referred to here are
(a) Ozone, CFCs
(b) CFCs, UV rays
(c) CFCs, Ozone
(d) UV rays, Diatomic Oxygen
Answer:
(c) CFCs, Ozone
Question 16.
Which of the following features relates to biodegradable substances?
(a) Broken down by biological processes
(b) Remain inert
(c) Persist in the environment for a long time
(d) May harm the ecosystem
Answer:
(a) Broken down by biological processes
Direction (Nos. 17-20) consists of two statements – Assertion (A) and Reason (R). Answer these questions by selecting the appropriate option given below.
(a) Both (A) and (R) are true and (R) is the correct explanation of (A).
(b) Both (A) and (R) are true but (R) is not the correct explanation of (A).
(c) (A) is true but (R) is false.
(d) (A) is false but (R) is true.
Question 17.
Assertion (A): Rusting of iron is endothermic.
Reason (R): As the reaction is slow, the release of heat is barely evident.
Answer:
(d) (A) is false, but (R) is true.
The correct form of (A) statement is The rusting of iron is exothermic.
Question 18.
Assertion (A): The probability of survival of an organism produced through sexual reproduction is more than that of an organism produced through asexual mode.
Reason (R): Variations provide advantages to individuals for survival.
Answer:
(a) Both (A) and (R) are true and (R) is the correct explanation of (A).
Question 19.
Assertion (A): A compass needle is placed near a current-carrying wire. The deflection of the compass needle decreases when the magnitude of the current in the wire is increased.
Reason (R): The strength of a magnetic field at a point near the conductor increases by increasing the current.
Answer:
(d) (A) is false, but (R) is true.
A compass needle is placed near a current-carrying wire. The deflection of the compass needle increases when the magnitude of the current in the wire is increased. Because the strength of a magnetic field at a point near the conductor increases with increasing the current.
Question 20.
Assertion (A): Biodegradable substances result in the formation of compost and natural replenishment.
Reason (R): It is due to the breakdown of complex inorganic substances into simple organic substances.
Answer:
(c) (A) is true but (R) is false
Reason can be corrected as During compost formation, complex organic substances are broken down into simple inorganic substances that go into the soil and are used by the plants.
Section B
Questions No. 21 to 26 are Very Short Answer Questions.
Question 21.
Dil. HCl is added to Zn granules. How will you prove that chemical change has taken place here? Support your response with two arguments.
Answer:
When zinc granules are added to dil. HC1, it leads to the formation of zinc chloride salt with the evolution of hydrogen gas. The evolved gas is colourless and odourless. Its chemical change can be detected by measuring the temperature change, by observing the change in colour of zinc from silver-grey to black, or by bubbles of gas.
Question 22.
State the post-fertilization changes that lead to fruit formation in plants.
Answer:
- After fertilization, the zygote divides to form an embryo within the ovule,
- The fertilized ovule forms a seed that is enclosed in a protective covering called the seed coat.
- As the seed grows further, the other floral parts such as petals, sepals stamens, style, and stigma may fall off.
- This leads to the growth of the ovary which enlarges and ripens to form a fruit.
Question 23.
What is the purpose of making urine in the human body? Name the organs that store and release the urine.
Or
Why do arteries have thick and elastic walls, whereas veins have valves?
Answer:
The main purpose of making urine in the body is to filter out nitrogenous waste products like urea and uric acid from the blood. The urinary bladder and urethra are the organs that store and release the urine, respectively.
Or
The blood emerges from the heart under high pressure and flows through arteries. Therefore, to resist this pressure, the arteries have thick and elastic walls. Veins have valves, which ensure that the blood flow occurs in one direction only.
Question 24.
The refractive indices of the three media are given below.
Medium | Refractive Index |
A | 1.6 |
B | 1.8 |
C | 1.5 |
A ray of light is travelling from A to B and another ray is travelling from B to C.
(i) In which of the two cases, the refracted ray bends towards the normal?
(ii) In which case, does the speed of light increase in the second medium?
Give reasons for your answer.
Answer:
(i) When light travels from an optically rarer medium to an optically denser medium, it moves towards the normal. Since nB > nA, hence the light ray will bend towards the normal on passing from medium A to B.
(ii) The speed of light will increase, when the light travels from B to C. Since, nC < nB and v = c/n, the speed of light ray will increase in the second medium.
Question 25.
A piece of wire of resistance R is cut into three equal parts. These parts are then connected in parallel. If the equivalent resistance of this parallel combination is R1, what is the value of the ratio R1 : R?
Or
Refer to the image below and state how the magnetic field pattern indicates regions, where the magnetic field is stronger outside the magnet. What happens to the magnetic field, when the current in the circuit is reversed?
Answer:
According to the question,
Resistance of each part = (R/3) Ω
Now, these parts are connected parallelly. So,
\(\frac{1}{R_1}=\frac{3}{R}+\frac{3}{R}+\frac{3}{R}=\frac{9}{R}\)
\(R_1=\frac{R}{9}\)
Hence, the ratio of \(\frac{R_1}{R}=\frac{1}{9}\) or R1 : R = 1 : 9.
Or
The magnetic field strength is more in the region, where the field lines are crowded. This means that the field strength is maximum near the poles and it reduces as we go away from the poles.
Question 26.
Study the food chain given below and answer the questions that follow.
(i) If the amount of energy available at the third trophic level is 100 J, then how much energy will be available at the producer level? Justify your answer.
(ii) Is it possible to have 2 more trophic levels in this food chain just before the fourth trophic level? Justify your answer.
Answer:
(i) According to the 10% law, only 10% energy is available for the next trophic level, Therefore, 10000 J energy will be available at the producer level.
(ii) No, the energy will be greatly lost at each step and very little usable energy will remain after four trophic levels.
Section C
Questions No. 27 to 33 are Short Answer Questions.
Question 27.
The given reaction shows one of the processes to extract the metals like iron and manganese.
MnO2 (s) + Al (s) → Mn (l) + Al2O3 (s) + Heat
(i) Give a reason why the above reaction is known as a thermite reaction.
(ii) Identify the substance oxidized and reduced in the above reaction.
(iii) Give a reason why aluminium is preferably used in thermite reactions.
Answer:
(i) A thermite reaction is an exothermic redox reaction. It is known for its ability to produce extreme heat upon ignition accompanied by light. That’s why it is known as a thermite reaction. The product obtained in this reaction is in a molten/ liquid state.
(ii)
The substance oxidized = Al (s)
The substance reduced = Mn in MnO2 (s)
(iii) Aluminium is preferably used in thermite reactions, as it is placed above Fe and Mn in the reactivity series of metals or we can say that, it is more reactive than Fe and Mn.
Question 28.
An element M with electronic configuration 2, 8, 3 combines separately with Cl–, \(\mathrm{SO}_4^{2-}\) anions. Write the chemical formulae of the compounds formed. Predict with the suitable reason the nature of the bond formed by element M in general. How will the electrical conductivity of the compounds formed vary concerning M?
Or
A reddish-brown metal X when heated in air, gives a black compound Y, which when heated in the presence of H2 gas gives X back. X is refined by the process of electrolysis; this refined form of X is used in electrical wiring. Identify X and Y. Draw a well-labeled diagram to represent the process of refining X.
Answer:
The electronic configuration of M = 2, 8, 3
M on combining separately with Cl– and \(\mathrm{SO}_4^{2-}\) form MCl3 and M2(SO4)3
M in general forms an ionic bond. It can acquire a stable configuration of neon (2, 8) by losing its three valence electrons to form M3+ cation.
The compounds formed will conduct electricity in the molten state but not in the solid state.
Or
The brown metal X is copper (Cu). When heated with air, it gives CuO (Y). The reaction involved is
2Cu + O2 → 2CuO
X is acquired back by reacting with H2.
CuO + H2 → Cu + H2O
The diagram to represent the process of refining X is as follows.
Question 29.
We are advised to take iodized salt in our diet by doctors. Justify its importance in our body.
Answer:
Iodine is required for the synthesis of thyroxine hormone. This hormone regulates fat, protein, and carbohydrate metabolism in our body. Deficiency of thyroxine leads to the enlargement of the thyroid gland. This deficiency disease is known as goiter. Therefore, we are advised to take iodized salt in our diet by doctors.
Question 30.
What is the probability of a girl or a boy being born into a family? Justify your answer.
Answer:
There is a 50% probability that a girl may be born and a 50% probability that a boy may be born in a family. It can be explained as,
- Humans have 22 pairs of autosomes and one pair of sex chromosomes.
- All females have a perfect pair of sex chromosomes XX, whereas males have a mismatched pair of sex chromosomes XY, in which one is a normal chromosome and the other is a short Y chromosome.
- A child receives one chromosome from the mother which is essentially X-chromosome.
- A child who inherits an X-chromosome from a father will be a girl and one who inherits a Y-chromosome will be a boy.
Question 31.
(i) Explain why the refractive index of any material concerning air is always greater than 1.
(ii) In the figure below, a light ray travels from the air into the semi-circular plastic block. Give a reason why the ray does not deviate at the semi-circular boundary of the plastic block.
(iii) Complete the ray diagram of the above scenario, when the light ray comes out of the plastic block from the top flat end.
Answer:
(i) The refractive index of a medium concerning air is given by
n = \(\frac{Speed of light in air}{Speed of light in the medium}\)
Since the speed of light in the medium is always less than the speed of light in air, the refractive index of any material concerning air is always greater than 1.
(ii) The ray of light is undergoing normal incidence at the air-plastic block interface and for normal incidence, there is no deviation.
(iii) As the light comes out of the plastic block from the top flat end, it moves away from the normal.
Question 32.
(i) State the law that explains the heating effect of current concerning the measurable properties in an electrical circuit.
(ii) List the factors on which the resistance of a conductor depends.
Answer:
(i) Joule’s law of heating states that the heat dissipated across a resistor is directly proportional to
- The square of current flowing through it.
- The resistance of the conductor.
- Time of flow of current, as H = i2Rt.
(ii) Resistance of a conductor depends on R = \(\frac{\rho L}{A}\)
- Length of conductor
- Area of cross-section
- Resistivity of conductor
Question 33.
Anannya responded to the question: Why are electrical appliances with metallic bodies connected to the mains through a three-pin plug, whereas an electric bulb can be connected with a two-pin plug?
She wrote: Three-pin connections reduce heating of connecting wires.
(i) Is her answer correct or incorrect? Justify.
(ii) What is the function of a fuse in a domestic circuit?
Answer:
(i) Anannya’s answer is incorrect. Electrical appliances with metallic bodies need an earth wire that provides a low-resistance conducting path to the flow of current. In case, there is an accidental leakage of current through the conducting body of the appliances.
(ii) An electrical fuse is a safety device that operates to protect against the overflow of current in an electrical circuit. An important component of an electrical fuse is a metal wire or strip that melts when excess current flows through it.
Section D
Questions No. 34 to 36 are Long Answer Questions.
Question 34.
(i) Rehmat classified the reaction between methane and chlorine in the presence of sunlight as a substitution reaction. Support Rehmat’s view with suitable justification and illustrate the reaction with the help of a balanced chemical equation.
(ii) Chlorine gas was prepared using electrolysis of brine solution. Write the chemical equation to represent the change. Identify the other products formed in the process and give one application of each.
Or
Raina while doing certain reactions observed that heating of substance X, with a vinegar-like smell, with a substance Y (which is used as an industrial solvent) in the presence of a cone, sulphuric acid in a water bath gives a sweet-smelling liquid Z having molecular soda (NaOH), Z gives back the sodium salt of X and the compound Y. Identify X, Y and Z. Illustrate the changes with the help of suitable chemical equations.
Answer:
(i) Rehmat’s observation is correct as the hydrogen atoms are substituted by hetero-atom, i.e. Cl.
CH4 + Cl2 → CH3Cl + HCl (in the presence of sunlight)
(ii) Net chemical equation to represent electrolysis of brine solution.
2NaCl (aq) + 2H2O (l) → 2NaOH (aq) + Cl2 (g) + H2 (g)
Other relevant equations are given below:
NaCl → Na+ + Cl–
2Cl– → Cl2 + 2e– (At anode)
H2O → H+ + OH–
2H+ + 2e– → H2 (At cathode)
Na+ + OH– → NaOH
Uses of the by-product formed in the reaction are as follows.
(i) Sodium hydroxide/NaOH/ Caustic soda
- Degreasing of metals
- Preparation of soaps and detergents
- Papermaking
- Artificial fibres
(ii) Hydrogen
- Fuels
- Margarine
- Manufacturing of ammonia for fertilizers
Or
The compound Z (C4H8O2) is an ester, as it has a sweet smell. According to the given molecular formula, the ester is ethyl ethanoate. i.e., CH3COOC2H5 (Z). It is given that, when Z is heated with NaOH, it gives a sodium salt of X. Thus, X is CH3COOH (its sodium salt is CH3COONa). The reaction involved is
As it is given that, X and Y react to give ester Z, thus Y is C2H5OH.
Thus, X, Y, and Z are ethanoic acid or acetic acid (CH3COOH), ethanol or ethyl alcohol (C2H5OH), and ethyl ethanoate (CH3COOC2H6).
Question 35.
Given below are certain situations. Analyse and describe its possible impact on a person
(i) Testes of a male boy are not able to descend into the scrotum during his embryonic development.
(ii) The vas deferens of a man is plugged.
(iii) Prostate and seminal vesicles are not functional.
(iv) Egg is not fertilized in a human female.
(v) The placenta does not attach to the uterus optimally.
Or
(i) A doctor has advised Sameer to reduce sugar intake in his diet and do regular exercise after checking his blood test reports. Which disease do you think Sameer is suffering from? Name the hormone responsible for this disease and the organ producing the hormone.
(ii) Which hormone is present in the areas of rapid cell division in a plant and which hormone inhibits the growth?
Answer:
(i) Formation of the sperm will be adversely affected because this process requires a lower temperature than the body temperature.
(ii) If the vas deferens of a man is plugged, sperms will not be transferred further because it is a passage for the transfer of sperms.
(iii) When prostate and seminal vesicles are not functional, they will not secrete fluid for nourishment and medium for the transport of sperms.
(iv) When an egg is not fertilized in a human female, it lives for about one day. Then, menstruation occurs in which the thickened lining of the uterus breaks leading to the discharge of blood and mucus along with the run fertilised egg.
(v) When the placenta does not attach to the uterus optimally, nutrition and oxygen will not be provided to the growing embryo affecting its growth.
Or
(i) Sameer is suffering from diabetes. Insulin is the hormone responsible for this disease and it is produced by the pancreas.
(ii) Cytokinins is present in the areas of rapid cell divisions in a plant and abscisic acid inhibits the growth.
Question 36.
The above image shows a thin lens with a focal length of 5m.
(i) What is the kind of lens shown in the above figure?
(ii) If a real inverted image is to be formed by this lens at a distance of 7m from the pole, then show with calculation, where should the object be placed.
(iii) Draw a neatly labelled diagram of the image formation mentioned in (ii).
Or
A 10 cm long pencil is placed 5 cm in front of a concave mirror having a radius of curvature of 40 cm.
(i) Determine the position of the image formed by this mirror.
(ii) What is the size of the image?
(iii) Draw a ray diagram to show the formation of the image as mentioned in part (i).
Answer:
(i) The lens used is a convex lens.
(ii) We know that, \(\frac{1}{f}=\frac{1}{v}-\frac{1}{u}\)
Given that, v = 7 m, f = 5 m.
So, from the above equation,
\(\frac{1}{5}=\frac{1}{7}-\frac{1}{u}\)
\(\frac{1}{u}=\frac{1}{7}-\frac{1}{5}=\frac{-2}{35}\)
u = \(\frac{-35}{2}\) = -17.5 m
The object will be placed 17.5 m on the left of the convex lens.
(iii)
The image is obtained at 6.67 cm behind the mirror.
(ii) According to the formula of magnification,
Section E
Questions No. 37 to 39 are case-based/data-based questions with 2 to 3 short sub-parts. Internal choice is provided in one of these sub-parts.
Question 37.
The table below shows the hints given by the quiz master in a quiz.
Hints |
(i) Substance C is used as a preservative. |
(ii) C has two carbon atoms; C is obtained by the reaction of A in the presence of alkaline potassium permanganate followed by acidification. |
(iii) Misuse of A in industries is prevented by adding methanol, benzene, and pyridine to A. |
(iv) F is formed on heating A in the presence of cone, sulphuric acid. |
(v) F reacts with hydrogen gas in the presence of nickel and palladium catalysts. |
Based on the above hints, answer the following questions.
(a) Give the IUPAC names of A and F.
(b) Illustrate with the help of chemical equations, the changes taking place. (A → C and A → F)
Or
Name the chemical reactions which occur in steps 2 and 5. Identify the compounds formed in these steps, if A is replaced with its next homologue.
Answer:
(a) The IUPAC name of A is ethanol and that of F is ethene.
Or
The name reactions involved in steps 2 and 5 are oxidation and addition (hydrogenation), respectively. The next homologue of (A) is propanol, Thus, propanol on heating with alkaline KMnO4 is propanoic acid. While Propanol reacts with hot concentrated form propene.
Question 38.
Figures (a) to (d) given below represent the type of ear lobes present in a family consisting of 2 children – Rahul, and Nisha and their parents.
Excited by his observation of different types of ear lobes present in his family, Rahul surveyed the type of ear lobes found [Figs, (e) and (f)] in his classmates. He found two types of ear lobes in his classmates as per the frequency given below.
Sex | Free | Attached |
Male | 36 | 14 |
Female | 31 | 19 |
Based on the above data, answer the following questions.
(i) Which of the two characteristics ‘free ear lobe’ or ‘attached ear lobe’ appears to be dominant in this case? Why?
(ii) Is the inheritance of the free ear lobe linked with the sex of the individual? Give a reason for your answer.
(iii) What type of ear lobe is present in father, mother, Rahul, and his sister Nisha? Write the genetic constitution of each of these family members which explains the inheritance of this character in this family.
(The gene for the free ear lobe is represented by F and the gene for the attached ear lobe is represented by for writing the generic constitution).
Or
Suresh’s parents have attached ear lobes. What type of ear lobe can be seen in Suresh and his sister Siya? Explain by giving the genetic composition of all.
Answer:
(i) The free ear lobe appears to be dominant in this case because a large majority of the population has this type of ear lobe.
(ii) No, it is not sex-linked. As per the data of the family as well as the class, it is observed that the free ear lobe is present in males as well as in females.
(iii)
Name | Type of Lobe | Genetic Constitution |
Father | Free ear lobe | Ff |
Mother | Free ear lobe | Ff |
Rahul | Attached ear lobe | Ff |
Nisha | Free ear lobe | Ff |
Or | ||
Parents | Attached ear lobe | Ff |
Suresh | Attached ear lobe | Ff |
Siya | Attached ear lobe | ff |
If both parents have recessive traits or characters, then all the children will have recessive characters only.
Question 39.
Vinita and Ahmed demonstrated a circuit that operates the two headlights and the two sidelights of a car, in their school exhibition. Based on their demonstrated circuit, answer the following questions.
(i) State what happens, when switch A is connected to
(a) Position 2
(b) Position 3
(ii) Find the potential difference across each lamp, when lit.
(iii) Calculate the current
(a) in each 12 Ω lamp, when lit.
(b) in each 4 Ω lamp, when lit.
Or
Show with calculations, which type of lamp, 4.0 Ω or 12 Ω has the higher power.
Answer:
(i) (a) When switch A is connected to position 2, then 12 Ω lamps will switch ON only.
(b) When switch A is connected to position 3, then 4 Ω lamps will switch ON.
(ii) All the lamps are connected parallel to each other, hence the potential difference will be 12V for all the lamps.
(a) 12 Ω lamps are ON when the wire is connected to position 2.
The voltage across both 12 Ω lamps = 12V
From V = IR (Ohm’s law),
I = \(\frac{V}{R}=\frac{12}{12}\) = 1A
(b) 4 Ω lamps are ON when the wire is connected to position 3.
The voltage across both 4 Ω lamps = 12 V
Hence, I = \(\frac{V}{R}=\frac{12}{4}\) = 3A
(iii) The power is given by P = \(\frac{V^2}{R}\)
All lamps are in parallel and hence V for all lamps are same.
For 4 Ω lamps, P = \(\frac{12 \times 12}{4}\) = 36 W
For 12 Ω lamps, P = \(\frac{12 \times 12}{12}\) = 12 W
Hence, 4 Ω lamps will have higher power.