▶️ Answer/Explanation
Plants photosynthesise using \(CO_2\) and water in the presence of light to build organic compounds.
They also need mineral ions (e.g. nitrate, magnesium) absorbed from the soil for growth and making chemicals such as proteins and chlorophyll.
Light energy itself, not organic compounds, is absorbed from outside — organic compounds are made, not taken in.
✅ Answer: (C)
They also need mineral ions (e.g. nitrate, magnesium) absorbed from the soil for growth and making chemicals such as proteins and chlorophyll.
Light energy itself, not organic compounds, is absorbed from outside — organic compounds are made, not taken in.
✅ Answer: (C)
▶️ Answer/Explanation
Distilled water has a higher water potential than the cell contents of the onion cells.
Water moves into the cells by osmosis, from the region of high water potential (distilled water) to the region of low water potential (cell sap).
As water enters, the cells swell and become turgid (they do not plasmolyse, since plasmolysis only occurs when cells lose water in a concentrated solution).
✅ Answer: (C)
Water moves into the cells by osmosis, from the region of high water potential (distilled water) to the region of low water potential (cell sap).
As water enters, the cells swell and become turgid (they do not plasmolyse, since plasmolysis only occurs when cells lose water in a concentrated solution).
✅ Answer: (C)
▶️ Answer/Explanation
Fats (lipids) are large molecules built from one molecule of glycerol combined with three fatty acid molecules.
Glycogen and starch are carbohydrates made of glucose units, and proteins are made of amino acids, so glycerol is not a component of these.
✅ Answer: (A)
Glycogen and starch are carbohydrates made of glucose units, and proteins are made of amino acids, so glycerol is not a component of these.
✅ Answer: (A)
▶️ Answer/Explanation
Enzymes such as salivary amylase have an optimum temperature at which their rate of reaction is highest.
Point X is on the falling part of the curve, after the peak rate has been reached, showing the rate is decreasing as temperature rises further.
This decline happens because the enzyme’s active site starts to lose its shape (denature) once the temperature goes above the optimum.
✅ Answer: (D)
Point X is on the falling part of the curve, after the peak rate has been reached, showing the rate is decreasing as temperature rises further.
This decline happens because the enzyme’s active site starts to lose its shape (denature) once the temperature goes above the optimum.
✅ Answer: (D)
▶️ Answer/Explanation
Chlorophyll is only made by plant cells that carry out photosynthesis, and magnesium ions are needed as a component of the chlorophyll molecule.
An animal cell does not photosynthesise and so has no chlorophyll to make, meaning it does not need magnesium ions for this purpose.
Cell A is the one shown to be an animal cell (lacking a cell wall and chloroplasts), so it is the correct choice.
✅ Answer: (A)
An animal cell does not photosynthesise and so has no chlorophyll to make, meaning it does not need magnesium ions for this purpose.
Cell A is the one shown to be an animal cell (lacking a cell wall and chloroplasts), so it is the correct choice.
✅ Answer: (A)
▶️ Answer/Explanation
Canine teeth are pointed and cone-shaped, used mainly for gripping and tearing food, unlike the flat-edged incisors or the ridged, flatter premolars and molars.
Of the four shapes shown, the tooth with a single sharp, pointed cusp and no flat biting or grinding surface matches this description.
This distinctive pointed shape identifies option D as the canine.
✅ Answer: (D)
Of the four shapes shown, the tooth with a single sharp, pointed cusp and no flat biting or grinding surface matches this description.
This distinctive pointed shape identifies option D as the canine.
✅ Answer: (D)
▶️ Answer/Explanation
Translocation is the transport of sugars made in the leaf to respiring tissues (and storage organs), and it occurs in the phloem.
Transpiration is the movement of water from the root up to the leaf, and it occurs in the xylem.
Only row C matches both of these correctly (translocation: leaf → respiring tissue via phloem; transpiration: root → leaf via xylem).
✅ Answer: (C)
Transpiration is the movement of water from the root up to the leaf, and it occurs in the xylem.
Only row C matches both of these correctly (translocation: leaf → respiring tissue via phloem; transpiration: root → leaf via xylem).
✅ Answer: (C)
▶️ Answer/Explanation
Aerobic respiration in animals and plants produces carbon dioxide and water as its only products, \( \text{glucose} + O_2 \rightarrow CO_2 + H_2O \).
Anaerobic respiration in animal muscle cells produces lactic acid only, while anaerobic respiration in yeast (alcoholic fermentation) produces alcohol and carbon dioxide.
The diagram that shows aerobic respiration giving only CO₂ and H₂O, and anaerobic respiration giving lactic acid, alcohol, and CO₂ correctly (matching the two separate anaerobic pathways), is the correct one.
✅ Answer: (D)
Anaerobic respiration in animal muscle cells produces lactic acid only, while anaerobic respiration in yeast (alcoholic fermentation) produces alcohol and carbon dioxide.
The diagram that shows aerobic respiration giving only CO₂ and H₂O, and anaerobic respiration giving lactic acid, alcohol, and CO₂ correctly (matching the two separate anaerobic pathways), is the correct one.
✅ Answer: (D)
▶️ Answer/Explanation
Gravitropism is a plant’s growth response to the direction of gravity.
A root growing downwards is growing in the direction of the gravitational pull, which is described as a positive response.
This is the opposite of a shoot, which grows upwards (negative gravitropism, but positive phototropism, towards light).
✅ Answer: (C)
A root growing downwards is growing in the direction of the gravitational pull, which is described as a positive response.
This is the opposite of a shoot, which grows upwards (negative gravitropism, but positive phototropism, towards light).
✅ Answer: (C)
▶️ Answer/Explanation
The placenta allows the exchange of substances such as oxygen, nutrients, and carbon dioxide between the mother’s blood and the fetus’s blood by diffusion, without the two blood supplies actually mixing.
It also acts as a barrier, blocking many (though not all) harmful substances and pathogens from reaching the fetus.
It does not cushion the fetus (that is the role of amniotic fluid) or maintain temperature, so the barrier function is the correct answer.
✅ Answer: (A)
It also acts as a barrier, blocking many (though not all) harmful substances and pathogens from reaching the fetus.
It does not cushion the fetus (that is the role of amniotic fluid) or maintain temperature, so the barrier function is the correct answer.
✅ Answer: (A)
▶️ Answer/Explanation
Meiosis halves the chromosome number of the parent cell, producing haploid cells (each with one set of chromosomes rather than two).
The original cell shown has 8 chromosomes (4 pairs), so the daughter cells produced by meiosis will have 4 chromosomes each.
Meiosis also involves crossing over and independent assortment, so the four cells produced are all genetically different from one another.
✅ Answer: (B)
The original cell shown has 8 chromosomes (4 pairs), so the daughter cells produced by meiosis will have 4 chromosomes each.
Meiosis also involves crossing over and independent assortment, so the four cells produced are all genetically different from one another.
✅ Answer: (B)
▶️ Answer/Explanation
Decomposers, such as bacteria and fungi, feed on dead organisms and organic waste (like faeces), breaking them down to release energy and recycle nutrients.
Producers make their own food by photosynthesis, while herbivores and carnivores feed on living plants or animals rather than dead remains.
This makes decomposers the only group that obtains energy specifically from dead organic matter.
✅ Answer: (B)
Producers make their own food by photosynthesis, while herbivores and carnivores feed on living plants or animals rather than dead remains.
This makes decomposers the only group that obtains energy specifically from dead organic matter.
✅ Answer: (B)
▶️ Answer/Explanation
Tree roots normally bind soil particles together and help it retain water, protecting it from being washed or blown away.
When trees are removed, the soil is left exposed and unprotected, so heavy rain and wind cause increased erosion and loss of the topsoil.
Deforestation does not increase atmospheric oxygen or release methane directly, and making land available for farming is generally seen as an intended benefit rather than an undesirable effect.
✅ Answer: (B)
When trees are removed, the soil is left exposed and unprotected, so heavy rain and wind cause increased erosion and loss of the topsoil.
Deforestation does not increase atmospheric oxygen or release methane directly, and making land available for farming is generally seen as an intended benefit rather than an undesirable effect.
✅ Answer: (B)
▶️ Answer/Explanation
Solids have fixed particle positions and cannot be compressed, while gas particles are far apart and can be squeezed closer together, so compressibility is a useful distinguishing property.
Solids have a definite melting point at which they turn to liquid, whereas a gas has no melting point (it would need to be cooled to become a liquid, then further to a solid), so melting point also distinguishes them.
Flammability depends on the chemical identity of the substance, not on its physical state, so it cannot be used to distinguish solids from gases.
✅ Answer: (A)
Solids have a definite melting point at which they turn to liquid, whereas a gas has no melting point (it would need to be cooled to become a liquid, then further to a solid), so melting point also distinguishes them.
Flammability depends on the chemical identity of the substance, not on its physical state, so it cannot be used to distinguish solids from gases.
✅ Answer: (A)
▶️ Answer/Explanation
The bottom number in the notation, 9, is the proton (atomic) number, which tells us the number of protons in the nucleus.
In a neutral atom, the number of electrons is always equal to the number of protons.
So this fluorine atom has 9 electrons; the top number, 19, is the nucleon (mass) number and is not used to find the electron count.
✅ Answer: (A)
In a neutral atom, the number of electrons is always equal to the number of protons.
So this fluorine atom has 9 electrons; the top number, 19, is the nucleon (mass) number and is not used to find the electron count.
✅ Answer: (A)
▶️ Answer/Explanation
Sodium chloride is formed by ionic bonding, in which sodium atoms transfer electrons to chlorine atoms, forming \(\text{Na}^+\) and \(\text{Cl}^-\) ions, not neutral atoms.
These oppositely charged ions are held together by strong electrostatic forces in a giant lattice, arranged in a highly regular, repeating pattern rather than randomly.
So the structure consists of a regular, alternating arrangement of sodium ions and chloride ions.
✅ Answer: (D)
These oppositely charged ions are held together by strong electrostatic forces in a giant lattice, arranged in a highly regular, repeating pattern rather than randomly.
So the structure consists of a regular, alternating arrangement of sodium ions and chloride ions.
✅ Answer: (D)
▶️ Answer/Explanation
Hydrogen has a relative atomic mass of 1, so 1 g of hydrogen (= 1 mole) contains \(6 \times 10^{23}\) atoms, which is the Avogadro constant.
Helium has a relative atomic mass of 4, meaning each helium atom is 4 times heavier than a hydrogen atom.
So 1 g of helium contains 4 times fewer atoms than 1 g of hydrogen: \(\frac{6 \times 10^{23}}{4} = 1.5 \times 10^{23}\).
✅ Answer: (A)
Helium has a relative atomic mass of 4, meaning each helium atom is 4 times heavier than a hydrogen atom.
So 1 g of helium contains 4 times fewer atoms than 1 g of hydrogen: \(\frac{6 \times 10^{23}}{4} = 1.5 \times 10^{23}\).
✅ Answer: (A)
▶️ Answer/Explanation
With inert carbon electrodes, copper(II) ions are discharged and deposited as copper metal at the cathode, but no copper ions re-enter the solution at the anode (oxygen or another gas is produced instead), so the concentration of copper(II) ions decreases.
With active copper electrodes, copper is deposited at the cathode exactly as copper dissolves from the copper anode into the solution, so these two processes balance out.
This means the concentration of copper(II) ions stays the same when copper electrodes are used, giving decreases / no change.
✅ Answer: (B)
With active copper electrodes, copper is deposited at the cathode exactly as copper dissolves from the copper anode into the solution, so these two processes balance out.
This means the concentration of copper(II) ions stays the same when copper electrodes are used, giving decreases / no change.
✅ Answer: (B)
▶️ Answer/Explanation
In an exothermic reaction, the products end up at a lower energy level than the reactants, because more energy is released forming new bonds than was absorbed breaking old ones, and this excess energy is transferred to the surroundings.
Activation energy is actually the minimum energy needed for a reaction to occur, not the maximum, and it stays fixed regardless of temperature (temperature instead increases the number of particles with at least this energy).
Bond forming always releases energy and is exothermic, not endothermic, so option B is also incorrect.
✅ Answer: (C)
Activation energy is actually the minimum energy needed for a reaction to occur, not the maximum, and it stays fixed regardless of temperature (temperature instead increases the number of particles with at least this energy).
Bond forming always releases energy and is exothermic, not endothermic, so option B is also incorrect.
✅ Answer: (C)
▶️ Answer/Explanation
Aluminium atoms lose electrons (are oxidised) to form \(\text{Al}^{3+}\) ions, so statement 4 is correct.
Iron(III) ions, \(\text{Fe}^{3+}\), gain electrons to become neutral iron atoms, meaning they are reduced, so statement 1 is correct.
Oxide ions, \(\text{O}^{2-}\), lose electrons to become oxygen atoms bound in \(\text{Al}_2\text{O}_3\) rather than gaining electrons, and since \(\text{Fe}_2\text{O}_3\) is itself reduced, it acts as the oxidising agent, not the reducing agent — so statements 2 and 3 are both incorrect.
✅ Answer: (B)
Iron(III) ions, \(\text{Fe}^{3+}\), gain electrons to become neutral iron atoms, meaning they are reduced, so statement 1 is correct.
Oxide ions, \(\text{O}^{2-}\), lose electrons to become oxygen atoms bound in \(\text{Al}_2\text{O}_3\) rather than gaining electrons, and since \(\text{Fe}_2\text{O}_3\) is itself reduced, it acts as the oxidising agent, not the reducing agent — so statements 2 and 3 are both incorrect.
✅ Answer: (B)
▶️ Answer/Explanation
Going down Group VII, the halogens change physical state at room temperature: chlorine is a gas, bromine is a liquid, and iodine is a solid, so they are not all gases.
All halogens do exist as diatomic molecules (e.g. \(\text{Cl}_2\), \( \text{I}_2\) and are classed as non-metals, and their colour does get darker going down the group (chlorine pale green, iodine dark grey/purple), so statements A, B and D are all true.
Since the question asks which statement is not correct, the false statement about them all being gases is the answer.
✅ Answer: (C)
All halogens do exist as diatomic molecules (e.g. \(\text{Cl}_2\), \( \text{I}_2\) and are classed as non-metals, and their colour does get darker going down the group (chlorine pale green, iodine dark grey/purple), so statements A, B and D are all true.
Since the question asks which statement is not correct, the false statement about them all being gases is the answer.
✅ Answer: (C)
▶️ Answer/Explanation
Filament lamps need an unreactive (inert) gas so that the hot metal filament does not react with it and burn out or oxidise.
Argon is a noble gas and is chemically inert, making it ideal for this purpose, and it is also cheap and readily available from the air.
Hydrogen and oxygen are reactive gases (hydrogen is flammable, oxygen supports combustion), so they would be unsuitable, while helium, although inert, is not the gas conventionally used in filament lamps.
✅ Answer: (A)
Argon is a noble gas and is chemically inert, making it ideal for this purpose, and it is also cheap and readily available from the air.
Hydrogen and oxygen are reactive gases (hydrogen is flammable, oxygen supports combustion), so they would be unsuitable, while helium, although inert, is not the gas conventionally used in filament lamps.
✅ Answer: (A)
▶️ Answer/Explanation
Alloys are mixtures, not compounds, since the metals are simply combined together without any fixed chemical formula or new chemical bonds forming between them.
Since all alloys are made of metals (with metallic bonding retained), all alloys still conduct electricity, just like the pure metals they are made from.
So gap 1 should be “mixtures” and gap 2 should be “All”.
✅ Answer: (C)
Since all alloys are made of metals (with metallic bonding retained), all alloys still conduct electricity, just like the pure metals they are made from.
So gap 1 should be “mixtures” and gap 2 should be “All”.
✅ Answer: (C)
▶️ Answer/Explanation
Zinc is more reactive than copper, so it displaces copper from aqueous copper sulfate: \(\text{Zn} + \text{CuSO}_4 \rightarrow \text{ZnSO}_4 + \text{Cu}\).
As colourless zinc sulfate replaces the blue copper sulfate solution, the blue colour fades to colourless, and reddish-brown copper metal is deposited.
Copper is less reactive than aluminium so cannot displace it (A is wrong), magnesium is more reactive than iron so magnesium oxide would not be reduced by iron (B is wrong), and copper is less reactive than potassium so cannot displace it from potassium oxide (C is wrong).
✅ Answer: (D)
As colourless zinc sulfate replaces the blue copper sulfate solution, the blue colour fades to colourless, and reddish-brown copper metal is deposited.
Copper is less reactive than aluminium so cannot displace it (A is wrong), magnesium is more reactive than iron so magnesium oxide would not be reduced by iron (B is wrong), and copper is less reactive than potassium so cannot displace it from potassium oxide (C is wrong).
✅ Answer: (D)
▶️ Answer/Explanation
In the Contact process, sulfur dioxide is converted to sulfur trioxide, \(2\text{SO}_2 + \text{O}_2 \rightleftharpoons 2\text{SO}_3\), using vanadium(V) oxide, \(\text{V}_2\text{O}_5\), as the catalyst — not iron, which is used in the Haber process instead.
The reaction is carried out at a temperature of around 450 °C, which gives a good balance between reaction rate and the position of the equilibrium.
This matches the temperature of 450 °C with the vanadium(V) oxide catalyst.
✅ Answer: (D)
The reaction is carried out at a temperature of around 450 °C, which gives a good balance between reaction rate and the position of the equilibrium.
This matches the temperature of 450 °C with the vanadium(V) oxide catalyst.
✅ Answer: (D)
▶️ Answer/Explanation
Limestone is heated (thermally decomposed) to manufacture calcium oxide, and its basic nature makes it useful for neutralising acidic industrial waste and treating acidic soil in farming.
Purifying water is normally done using processes like filtration, sedimentation, or chlorination, not through the use of limestone.
So purifying water is the option that is not an actual use of limestone.
✅ Answer: (C)
Purifying water is normally done using processes like filtration, sedimentation, or chlorination, not through the use of limestone.
So purifying water is the option that is not an actual use of limestone.
✅ Answer: (C)
▶️ Answer/Explanation
Chloroethene, \(\text{CH}_2\text{=CHCl}\), undergoes addition polymerisation, in which the C=C double bond opens up and monomer units join together with only single bonds between carbon atoms.
The repeat unit keeps every atom from the monomer (2 carbons, 3 hydrogens, 1 chlorine per unit), joined in a long chain, ( \(-\text{CH}_2\text{-CHCl}_n-\) ).
The correct structure must show a chain of repeating \(-\text{CH}_2\text{-CHCl}-\) units with single bonds only and no atoms lost, which corresponds to option A.
✅ Answer: (A)
The repeat unit keeps every atom from the monomer (2 carbons, 3 hydrogens, 1 chlorine per unit), joined in a long chain, ( \(-\text{CH}_2\text{-CHCl}_n-\) ).
The correct structure must show a chain of repeating \(-\text{CH}_2\text{-CHCl}-\) units with single bonds only and no atoms lost, which corresponds to option A.
✅ Answer: (A)
▶️ Answer/Explanation
Acceleration is calculated using \( a = \dfrac{\text{change in velocity}}{\text{time taken}} \).
The change in velocity is \(35 – 20 = 15\) m/s, and the time taken is 5.0 s.
So \( a = \dfrac{15}{5.0} = 3.0 \) m/s².
✅ Answer: (A)
The change in velocity is \(35 – 20 = 15\) m/s, and the time taken is 5.0 s.
So \( a = \dfrac{15}{5.0} = 3.0 \) m/s².
✅ Answer: (A)
▶️ Answer/Explanation
Density is calculated as \( \rho = \dfrac{\text{mass}}{\text{volume}} \), so both mass and volume need to be measured.
A balance is used to find the mass of the metal, while a measuring cylinder is used to find its volume by the displacement of water when the metal is submerged.
A metre rule cannot measure the volume of an irregular shape (only regular ones), so it is not suitable here.
✅ Answer: (A)
A balance is used to find the mass of the metal, while a measuring cylinder is used to find its volume by the displacement of water when the metal is submerged.
A metre rule cannot measure the volume of an irregular shape (only regular ones), so it is not suitable here.
✅ Answer: (A)
▶️ Answer/Explanation
The diagram shows the 7.0 N and 3.0 N forces acting in opposite directions on the object, so the resultant force is found by subtracting them: \(7.0 – 3.0 = 4.0\) N.
Using \( F = ma \), the acceleration is found by rearranging to \( a = \dfrac{F}{m} \).
So \( a = \dfrac{4.0}{2.0} = 2.0 \) m/s².
✅ Answer: (C)
Using \( F = ma \), the acceleration is found by rearranging to \( a = \dfrac{F}{m} \).
So \( a = \dfrac{4.0}{2.0} = 2.0 \) m/s².
✅ Answer: (C)
▶️ Answer/Explanation
A battery stores energy in the form of chemical potential energy within its internal chemicals.
When connected in a circuit, a chemical reaction inside the battery releases this energy and drives electrons around the circuit, transferring chemical energy into electrical energy.
A lamp, electric motor, and television all take electrical energy in and convert it to other forms (light/heat, kinetic, and light/sound respectively), rather than producing electrical energy.
✅ Answer: (A)
When connected in a circuit, a chemical reaction inside the battery releases this energy and drives electrons around the circuit, transferring chemical energy into electrical energy.
A lamp, electric motor, and television all take electrical energy in and convert it to other forms (light/heat, kinetic, and light/sound respectively), rather than producing electrical energy.
✅ Answer: (A)
▶️ Answer/Explanation
In a hydroelectric power station, water is held at a height behind a dam, giving it gravitational potential energy.
As the water falls, this gravitational potential energy is converted into kinetic energy, which turns turbines connected to generators.
The generators then transfer this kinetic energy into electrical energy, so the original energy source is gravitational potential energy.
✅ Answer: (C)
As the water falls, this gravitational potential energy is converted into kinetic energy, which turns turbines connected to generators.
The generators then transfer this kinetic energy into electrical energy, so the original energy source is gravitational potential energy.
✅ Answer: (C)
▶️ Answer/Explanation
In a solid, particles are held tightly in fixed positions by strong forces, so heating only causes small increases in vibration and expansion.
In a liquid, particles are more loosely arranged and can move past each other, allowing for greater expansion than a solid for the same temperature rise.
Gas particles are far apart and move freely with weak forces between them, so they expand by far the greatest amount when heated, since their spacing increases much more easily.
✅ Answer: (A)
In a liquid, particles are more loosely arranged and can move past each other, allowing for greater expansion than a solid for the same temperature rise.
Gas particles are far apart and move freely with weak forces between them, so they expand by far the greatest amount when heated, since their spacing increases much more easily.
✅ Answer: (A)
▶️ Answer/Explanation
Since light travels faster in air than in diamond, diamond is the optically denser medium, so light passing from diamond into air bends away from the normal, making the angle in air larger than the angle in diamond.
The angle of incidence in the diamond must also be smaller than the critical angle (25°) for the light to refract into the air rather than undergo total internal reflection.
The diagram showing a small angle inside the diamond (below 25°) refracting to a larger angle in the air, bending away from the normal, is the correct one.
✅ Answer: (D)
The angle of incidence in the diamond must also be smaller than the critical angle (25°) for the light to refract into the air rather than undergo total internal reflection.
The diagram showing a small angle inside the diamond (below 25°) refracting to a larger angle in the air, bending away from the normal, is the correct one.
✅ Answer: (D)
▶️ Answer/Explanation
An electromagnet’s magnetic field is created by an electric current flowing through a coil of wire, so its magnetism can be turned on or off very rapidly simply by switching the current on or off.
A permanent magnet keeps its magnetism at all times and cannot be switched off, so it cannot be used in this way.
This makes an electromagnet the only type of magnet suitable for switching on and off many times per second.
✅ Answer: (A)
A permanent magnet keeps its magnetism at all times and cannot be switched off, so it cannot be used in this way.
This makes an electromagnet the only type of magnet suitable for switching on and off many times per second.
✅ Answer: (A)
▶️ Answer/Explanation
For a wire made of the same material, resistance is proportional to length and inversely proportional to cross-sectional area, \( R \propto \dfrac{l}{A} \).
To have the same resistance (R) as the original wire, a new wire must have the same ratio of length to area — for example, doubling both the length and the area leaves the ratio (and hence the resistance) unchanged.
Based on the dimensions shown in the diagram, wire Y has a length-to-area ratio equal to the original wire, giving it the same resistance (R).
✅ Answer: (B)
To have the same resistance (R) as the original wire, a new wire must have the same ratio of length to area — for example, doubling both the length and the area leaves the ratio (and hence the resistance) unchanged.
Based on the dimensions shown in the diagram, wire Y has a length-to-area ratio equal to the original wire, giving it the same resistance (R).
✅ Answer: (B)
▶️ Answer/Explanation
Since the lamps are in parallel, the voltage across each lamp equals the battery e.m.f., 10V, so the power of lamp Y is \( P_Y = IV = 2.0 \times 10 = 20 \) W.
Since the power of Y is half the power of X, the power of lamp X is \( P_X = 2 \times 20 = 40 \) W, giving a current in X of \( I_X = \dfrac{40}{10} = 4.0 \) A.
The total current supplied by the battery is \( 2.0 + 4.0 = 6.0 \) A, so total power is \( 10 \times 6.0 = 60 \) W, and energy transferred in 60 s is \( 60 \times 60 = 3600 \) J.
✅ Answer: (D)
Since the power of Y is half the power of X, the power of lamp X is \( P_X = 2 \times 20 = 40 \) W, giving a current in X of \( I_X = \dfrac{40}{10} = 4.0 \) A.
The total current supplied by the battery is \( 2.0 + 4.0 = 6.0 \) A, so total power is \( 10 \times 6.0 = 60 \) W, and energy transferred in 60 s is \( 60 \times 60 = 3600 \) J.
✅ Answer: (D)
▶️ Answer/Explanation
A fuse must have a current rating higher than the normal operating current of the appliance, so that it does not blow during ordinary use.
Since the heater draws 11A, a 3A or 10A fuse would melt (blow) even under normal conditions, disconnecting the heater unnecessarily.
A 13A fuse is the smallest standard rating above 11A, so it lets the heater run normally but still melts quickly if a fault causes an excessive current, making it the most appropriate choice (36A would be far too high to offer proper protection).
✅ Answer: (C)
Since the heater draws 11A, a 3A or 10A fuse would melt (blow) even under normal conditions, disconnecting the heater unnecessarily.
A 13A fuse is the smallest standard rating above 11A, so it lets the heater run normally but still melts quickly if a fault causes an excessive current, making it the most appropriate choice (36A would be far too high to offer proper protection).
✅ Answer: (C)
▶️ Answer/Explanation
When a current-carrying wire is placed in a magnetic field, it experiences a force due to the motor effect, acting perpendicular to both the current direction and the magnetic field direction.
Using Fleming’s left-hand rule — First finger for Field (N to S), seCond finger for Current, thuMb for the resulting Motion (force) — the direction of the force can be worked out from the diagram’s field and current directions.
Applying this rule to the directions shown in the diagram gives a force acting in the direction labelled B.
✅ Answer: (B)
Using Fleming’s left-hand rule — First finger for Field (N to S), seCond finger for Current, thuMb for the resulting Motion (force) — the direction of the force can be worked out from the diagram’s field and current directions.
Applying this rule to the directions shown in the diagram gives a force acting in the direction labelled B.
✅ Answer: (B)
▶️ Answer/Explanation
Isotopes are atoms of the same element, meaning they must have the same number of protons, but they have different numbers of neutrons.
This means the correct pair of nuclei must show an equal number of protons in both nuclei, while the number of neutrons differs between them.
Checking each option against the key for protons and neutrons, the pair with matching proton counts but differing neutron counts is option B.
✅ Answer: (B)
This means the correct pair of nuclei must show an equal number of protons in both nuclei, while the number of neutrons differs between them.
Checking each option against the key for protons and neutrons, the pair with matching proton counts but differing neutron counts is option B.
✅ Answer: (B)