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General science and life science (up to CBSE Class 10) MCQ with Answers

18 questionswith explanationsfor RAS, Patwari, VDO and other Rajasthan exams

Questions

Q1

Consider the following statements about a long current-carrying solenoid: 1. The magnetic field inside it is uniform, with parallel field lines. 2. The field inside becomes stronger when the current is increased. 3. The field outside it is as strong as the field inside. Which of the statements given above are correct?

  1. (1)1 and 2 only
  2. (2)2 and 3 only
  3. (3)1 and 3 only
  4. (4)1, 2 and 3

Answer: (1) 1 and 2 only

Explanation

Inside a solenoid the field lines are parallel straight lines, so the field is uniform, and it grows with the current (and with the number of turns per unit length). Outside, the field resembles that of a bar magnet and is weak, so statement 3 is wrong; a soft-iron core inside makes an electromagnet. (NCERT Class 10 Science, Magnetic Effects of Electric Current: field due to a current in a solenoid.)

Q2

A positively charged particle moving towards the west is deflected towards the north by a magnetic field. The direction of the magnetic field is:

  1. (1)Downward
  2. (2)Towards the east
  3. (3)Upward
  4. (4)Towards the south

Answer: (3) Upward

Explanation

Use Fleming's left-hand rule: the motion of a positive charge is a current towards the west (middle finger) and the force is towards the north (thumb), so the forefinger, the field, points upward. A downward field would push the same particle towards the south. (NCERT Class 10 Science, Magnetic Effects of Electric Current: force on a current-carrying conductor in a magnetic field.)

Q3

If the distance between two objects is doubled while their masses stay the same, the gravitational force between them becomes:

  1. (1)Half
  2. (2)One-fourth
  3. (3)Twice
  4. (4)Four times

Answer: (2) One-fourth

Explanation

By the universal law of gravitation F = G m₁m₂/d², the force varies inversely as the square of the distance, so doubling d makes d² four times and F one-fourth. 'Half' would be right only if F varied as 1/d; doubling one of the masses, by contrast, doubles the force. (NCERT Class 9 Science, topic: universal law of gravitation.)

Q4

To reduce excessive reverberation in a large auditorium, its walls and ceiling are fitted with:

  1. (1)Smooth marble or glass panels
  2. (2)Curved, hard sounding boards behind the speaker
  3. (3)Smooth concrete surfaces
  4. (4)Sound-absorbing materials such as curtains and fibreboard

Answer: (4) Sound-absorbing materials such as curtains and fibreboard

Explanation

Reverberation is the persistence of sound because of repeated reflections from walls, ceiling and floor; rough, soft absorbers such as curtains, carpets and compressed fibreboard cut it. Curved sounding boards do the opposite job, reflecting sound towards the audience. A separate echo needs a reflector at least about 17 m away. (NCERT Class 9 Science, topic: reflection of sound and reverberation.)

Q5

How much work is done in moving a charge of 2 C from a point at a potential of 118 V to a point at a potential of 128 V?

  1. (1)5 J
  2. (2)236 J
  3. (3)20 J
  4. (4)256 J

Answer: (3) 20 J

Explanation

The potential difference between the points is 128 − 118 = 10 V, and W = QV = 2 × 10 = 20 J, since 1 volt is 1 joule of work per coulomb. 256 J uses the 128 V of the end point alone and ignores the starting potential; 5 J wrongly divides V by Q. (NCERT Class 10 Science, Electricity: electric potential and potential difference.)

Q6

A car of mass 1,200 kg moving at 72 km/h is brought to rest by its brakes in 6 s. The average braking force on the car is:

  1. (1)2,000 N
  2. (2)4,000 N
  3. (3)8,000 N
  4. (4)14,400 N

Answer: (2) 4,000 N

Explanation

72 km/h = 20 m/s, so the change in momentum is 1,200 × 20 = 24,000 kg m/s; by the second law, force = rate of change of momentum = 24,000 ÷ 6 = 4,000 N (a retardation of about 3.3 m/s²). 14,400 N comes from using 72 without converting km/h to m/s. (NCERT Class 9 Science, topic: second law of motion.)

Q7

Which of the following is NOT an exothermic process?

  1. (1)Adding water to quicklime
  2. (2)Burning of natural gas
  3. (3)Decomposition of vegetable matter into compost
  4. (4)Decomposition of ferrous sulphate crystals on heating

Answer: (4) Decomposition of ferrous sulphate crystals on heating

Explanation

Ferrous sulphate breaks down into ferric oxide, sulphur dioxide and sulphur trioxide only while it is heated, so this thermal decomposition is endothermic, as most decomposition reactions are. Quicklime reacting with water to form slaked lime releases a large amount of heat, and natural gas (methane) burning and vegetable matter rotting into compost also give out heat; NCERT lists compost-making as exothermic. (NCERT Class 10 Science, Chemical Reactions and Equations: exothermic and endothermic reactions.)

Q8

Which of the following is NOT a property of ionic compounds?

  1. (1)They conduct electricity in the solid state
  2. (2)They generally have high melting and boiling points
  3. (3)They conduct electricity in the molten state
  4. (4)They are generally soluble in water

Answer: (1) They conduct electricity in the solid state

Explanation

In the solid state the ions are locked in a rigid lattice and cannot move, so ionic compounds do not conduct; when molten or dissolved the ions become free and carry current. Strong electrostatic attraction gives them high melting points (NaCl melts at about 801 °C). (NCERT Class 10 Science, Metals and Non-metals: properties of ionic compounds.)

Q9

In the electrolytic refining of copper, a thick block of impure copper is connected to the positive terminal. The insoluble impurities that collect below this block are called:

  1. (1)Slag
  2. (2)Gangue
  3. (3)Anode mud
  4. (4)Flux

Answer: (3) Anode mud

Explanation

The impure copper is the anode, a thin strip of pure copper the cathode and acidified copper sulphate solution the electrolyte; pure copper from the anode is deposited on the cathode, soluble impurities go into the solution and insoluble ones settle below the anode as anode mud. Gangue, by contrast, is the earthy impurity (soil, sand) in an ore, removed before the metal is extracted. (NCERT Class 10 Science, Metals and Non-metals: refining of metals.)

Q10

In Rutherford's alpha-particle scattering experiment, nearly all the alpha particles passed straight through the gold foil, but about one in 12,000 bounced back. This showed that:

  1. (1)All the positive charge and most of the mass of an atom lie in a very small nucleus
  2. (2)Electrons revolve only in orbits of fixed energy
  3. (3)Positive charge is spread uniformly throughout the atom
  4. (4)Atoms are solid and indivisible spheres

Answer: (1) All the positive charge and most of the mass of an atom lie in a very small nucleus

Explanation

Since nearly all the particles went straight through, most of an atom is empty space, while the few that rebounded had met a tiny, dense, positively charged centre, the nucleus. Fixed orbits were added later by Bohr, and uniform positive charge was Thomson's model, which this result ruled out. (NCERT Class 9 Science, topic: Rutherford's model of the atom.)

Q11

An atom of aluminium has atomic number 13 and mass number 27. The numbers of protons, electrons and neutrons in it are, respectively:

  1. (1)13, 14, 13
  2. (2)13, 13, 14
  3. (3)14, 13, 13
  4. (4)13, 13, 27

Answer: (2) 13, 13, 14

Explanation

The atomic number gives the protons (13), and a neutral atom has as many electrons (13); neutrons = mass number − atomic number = 27 − 13 = 14, because the mass number counts protons and neutrons together. Taking 27 as the neutron count forgets that the protons are included in it. (NCERT Class 9 Science, topic: atomic number and mass number.)

Q12

Match List-I (element) with List-II (exception to the usual properties of metals and non-metals): List-I: A. Iodine B. Gallium C. Sodium D. Bromine List-II: i. A metal soft enough to be cut with a knife ii. A non-metal that is a liquid at room temperature iii. A metal that melts when kept on the palm iv. A non-metal that is lustrous

  1. (1)A-iv, B-i, C-iii, D-ii
  2. (2)A-ii, B-iii, C-i, D-iv
  3. (3)A-iv, B-iii, C-ii, D-i
  4. (4)A-iv, B-iii, C-i, D-ii

Answer: (4) A-iv, B-iii, C-i, D-ii

Explanation

Iodine is a non-metal yet lustrous; gallium (and caesium) have such low melting points that they melt on the palm; alkali metals such as sodium and potassium are soft enough to cut with a knife; and bromine is the non-metal that is a liquid at room temperature. The code with A-ii swaps iodine and bromine: both are halogens, but iodine is a solid. (NCERT Class 10 Science, Metals and Non-metals: physical properties.)

Q13

Stomatal pores in a leaf close when the guard cells:

  1. (1)Take in water and swell
  2. (2)Produce more starch
  3. (3)Lose water and shrink
  4. (4)Divide rapidly

Answer: (3) Lose water and shrink

Explanation

Water flowing into the guard cells makes them swell and open the pore for gas exchange; when they lose water they shrink and the pore closes, which saves water when it is scarce. Most of the water a plant loses by transpiration leaves through these pores. (NCERT Class 10 Science, Life Processes: nutrition in plants.)

Q14

Tendrils of a pea plant coil around a support because the cells of the tendril:

  1. (1)Away from the support grow faster than those in contact with it
  2. (2)In contact with the support grow faster than those away from it
  3. (3)Move towards light by growing more on the lighted side
  4. (4)Divide only at the tip of the tendril

Answer: (1) Away from the support grow faster than those in contact with it

Explanation

A tendril is sensitive to touch: the side that touches the support grows less, while the side away from it grows faster, so the tendril curls around the support. Bending towards light works differently, with auxin making the shaded side grow longer. (NCERT Class 10 Science, Control and Coordination: movement in plants.)

Q15

Consider the following statements about breathing in humans: 1. During inhalation the diaphragm relaxes and moves upwards. 2. During inhalation the ribs move up and outwards, enlarging the chest cavity. 3. During exhalation the diaphragm relaxes and returns to its dome shape. Which of the statements given above are correct?

  1. (1)1 and 2 only
  2. (2)2 and 3 only
  3. (3)1 and 3 only
  4. (4)1, 2 and 3

Answer: (2) 2 and 3 only

Explanation

On inhalation the diaphragm contracts and flattens (moves down) while the ribs lift up and out, so the chest cavity enlarges and air rushes in. On exhalation the diaphragm relaxes and regains its dome shape and the ribs drop. Statement 1 reverses the diaphragm's action. (NCERT Class 10 Science, Life Processes: respiration in human beings.)

Q16

Nitrogenous wastes such as urea are removed from the blood of a kidney patient in an artificial kidney (haemodialysis) mainly by:

  1. (1)Filtration under high pressure followed by selective reabsorption, as in a nephron
  2. (2)Active transport of urea using energy supplied by the machine
  3. (3)Chemical breakdown of urea by enzymes in the dialysing fluid
  4. (4)Diffusion across a semi-permeable membrane into the dialysing fluid

Answer: (4) Diffusion across a semi-permeable membrane into the dialysing fluid

Explanation

The patient's blood flows through tubes with a semi-permeable lining kept in a tank of dialysing fluid that has the same osmotic pressure as blood but no nitrogenous waste, so urea diffuses out and the cleaned blood is pumped back into the body. Unlike a nephron, the device involves no reabsorption, which rules out the filtration-and-reabsorption option. (NCERT Class 10 Science, Life Processes: excretion in human beings, artificial kidney.)

Q17

The shrinkage of the cell contents of a plant cell away from its cell wall when it is kept in a concentrated salt solution is called:

  1. (1)Endosmosis
  2. (2)Imbibition
  3. (3)Plasmolysis
  4. (4)Turgidity

Answer: (3) Plasmolysis

Explanation

In a hypertonic solution water leaves the cell by osmosis, so the cytoplasm shrinks away from the cell wall: plasmolysis. In a hypotonic solution, such as raisins soaked in plain water, water enters, the cell swells and becomes turgid. Endosmosis is the inward movement of water. (NCERT Class 9 Science, topic: osmosis and plasmolysis.)

Q18

Besides draining excess fluid from the spaces between cells back into the blood, lymph carries which of the following from the small intestine?

  1. (1)Amino acids from digested proteins
  2. (2)Digested and absorbed fat
  3. (3)Oxygen bound to haemoglobin
  4. (4)Urea on its way to the kidneys

Answer: (2) Digested and absorbed fat

Explanation

Lymph, a colourless fluid like plasma but with less protein, enters lymphatic capillaries and carries digested and absorbed fat from the intestine, besides returning excess tissue fluid to the blood. Amino acids and glucose pass into the blood capillaries of the villi instead, and lymph carries no oxygen on haemoglobin because it has no red blood cells. (NCERT Class 10 Science, Life Processes: transportation, lymph.)