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Q1. The passage of an electric current through a conducting liquid causes:
When electric current passes through a conducting liquid, it causes chemical effects. This includes the decomposition of the liquid and the deposition of metals on electrodes (electroplating). This is the basis of many industrial processes like electroplating and electrolysis. Magnetic and heating effects are also produced in conductors, but the chemical effect is the specific effect observed in conducting liquids.
Q2. Which of the following liquids is most likely to conduct electricity?
Lemon juice is an acid and contains ions that allow it to conduct electricity. Distilled water and sugar solutions are poor conductors, and vegetable oil is an insulator. Acids, bases, and salt solutions conduct electricity because they contain free ions that carry charge.
Q3. A material that allows electric current to pass through it is called:
A conductor is a material that allows electric current to pass through it easily. Metals like copper and aluminium are good conductors. Insulators do not allow current to pass, resistors oppose current flow, and semiconductors have intermediate conductivity.
Q4. The device that glows when even a weak electric current flows through it is:
An LED (Light Emitting Diode) glows even when a weak electric current flows through it. It is more sensitive than a bulb and is used in conductivity testers. A bulb requires a higher current to glow, and heaters and motors are not used to detect current.
Q5. In an LED, the longer lead (wire) is always connected to the:
The longer lead of an LED is always connected to the positive terminal of the battery. The shorter lead is connected to the negative terminal. This polarity must be observed for the LED to glow. If reversed, the LED will not light up.
Q6. Which of the following is a poor conductor of electricity?
Distilled water is a poor conductor of electricity because it does not contain any dissolved ions. Copper wire, salt water, and iron rods are good conductors. Water conducts electricity only when it contains dissolved salts or minerals that provide ions.
Q7. The process of depositing a layer of one metal on another metal using electricity is called:
Electroplating is the process of depositing a layer of one metal on another metal using electricity. It is used to prevent rusting, improve appearance, and make objects shiny. Galvanisation is coating iron with zinc using a different method (hot dipping), crystallisation is a separation technique, and rusting is corrosion.
Q8. Which of the following is an example of an electroplated object?
Iron gates coated with zinc is an example of electroplating (galvanisation is often done by electroplating). This prevents rusting. Wooden chairs, plastic bottles, and cotton shirts are not electroplated because they are not metals and do not conduct electricity.
Q9. The electrodes used in electroplating are:
Electroplating requires both a cathode (the object to be plated) and an anode (the metal to be deposited). Both electrodes are immersed in an electrolyte solution and connected to a battery. Current flows through the circuit, causing metal ions to deposit on the cathode.
Q10. Tap water conducts electricity because it contains:
Tap water conducts electricity because it contains dissolved minerals and salts that provide ions. These ions allow the water to conduct current. Distilled water, which lacks these dissolved substances, is a poor conductor. Dissolved oxygen, chlorine gas, and hydrogen gas do not contribute to conductivity.
Q11. In an electric circuit testing the conductivity of a liquid, if the bulb glows, the liquid is:
If the bulb glows in a conductivity tester, the liquid is a good conductor of electricity. This means it contains ions that allow current to flow. Insulators and poor conductors would not allow the bulb to glow. Non-electrolytes do not conduct electricity.
Q12. Which of the following is NOT a good conductor of electricity?
Pure water (distilled water) is NOT a good conductor of electricity because it has no free ions. Vinegar (acid), baking soda solution (base), and lemon juice (acid) all contain ions and conduct electricity. Pure water is an insulator, but it becomes conductive when salts are added.
Q13. The full form of LED is:
LED stands for Light Emitting Diode. It is a semiconductor device that emits light when an electric current passes through it. LEDs are energy-efficient and are used in indicator lights, displays, and lighting. They have polarity and glow with weak current.
Q14. Which electrode is connected to the negative terminal of the battery?
The cathode is the electrode connected to the negative terminal of the battery. The anode is connected to the positive terminal. In electrolysis and electroplating, positive ions (cations) move towards the cathode, and negative ions (anions) move towards the anode.
Q15. Electroplating helps in:
Electroplating is used to prevent rusting (corrosion) and to make objects shiny and decorative. It also makes objects more durable. It does not make objects heavier in a practical sense, nor does it dissolve metals. Electroplating deposits a thin layer of metal on the object.
Q16. Which of the following liquids is a good conductor of electricity?
A salt solution in distilled water is a good conductor of electricity because the salt dissolves to form ions. Sugar solution, alcohol, and kerosene do not produce ions and are poor conductors. Conductivity requires the presence of free ions in the solution.
Q17. In an LED, the shorter lead is connected to the:
The shorter lead of an LED is connected to the negative terminal of the battery. The longer lead is connected to the positive terminal. This polarity must be respected for the LED to glow. Connecting it incorrectly will prevent it from lighting up.
Q18. Which of the following objects is commonly electroplated with chromium?
Bicycle handlebars and car bumpers are commonly electroplated with chromium to make them shiny and resistant to corrosion. Iron nails are often galvanised with zinc, plastic toys and wooden boxes cannot be electroplated because they are non-conductors.
Q19. The liquid that conducts electricity is called:
An electrolyte is a liquid that conducts electricity because it contains ions. Examples include salt solution, acid solutions, and base solutions. Insulators do not conduct, conductors are general terms for materials, and solvents dissolve substances but may not conduct.
Q20. Which of the following does NOT conduct electricity?
Distilled water does not conduct electricity because it contains no dissolved ions. Copper sulphate solution, hydrochloric acid solution, and sea water all contain ions and conduct electricity. Distilled water is an insulator until salts are dissolved in it.
Q21. The electrode connected to the positive terminal of the battery is called:
The anode is the electrode connected to the positive terminal of the battery. The cathode is connected to the negative terminal. In electrolysis, anions (negative ions) move towards the anode, and cations (positive ions) move towards the cathode.
Q22. Electroplating is based on which effect of electric current?
Electroplating is based on the chemical effect of electric current. When current passes through an electrolyte, chemical reactions occur at the electrodes, depositing metal ions on the cathode. The heating effect and magnetic effect are not involved in electroplating.
Q23. Which of the following is an example of a poor conductor of electricity?
Distilled water is a poor conductor of electricity because it has no free ions. Rain water, well water, and tap water contain dissolved minerals that make them conductive. Pure water is an insulator, but it becomes conductive when impurities are dissolved.
Q24. The colour of light emitted by a standard red LED is:
A standard red LED emits red light. LEDs are available in different colours depending on the semiconductor material used. The colour of the LED is determined by the material composition, not by the current or voltage applied. Red LEDs are commonly used in indicator lights.
Q25. Which metal is commonly used to electroplate iron to prevent rusting?
Zinc is commonly used to electroplate iron to prevent rusting. This process is called galvanisation. Zinc is more reactive than iron and corrodes first, protecting the iron underneath. Copper, silver, and gold are also used for electroplating but for different purposes.
Q26. A solution that does not allow electricity to pass through is called:
An insulator is a solution or material that does not allow electricity to pass through it because it lacks free ions. Examples include distilled water, sugar solution, and oil. Electrolytes conduct electricity, conductors allow current, and electrodes are metal rods used in circuits.
Q27. In an electroplating experiment, the object to be plated is made the:
In electroplating, the object to be plated is made the cathode (negative electrode). The metal to be deposited is made the anode (positive electrode). Metal ions from the anode dissolve into the electrolyte and are deposited on the cathode, plating it.
Q28. Which of the following is an electroplated object commonly found in homes?
A stainless steel spoon is often an iron spoon plated with nickel or chromium to prevent rust and give it a shiny finish. Plastic buckets, glass tumblers, and wooden tables are not electroplated because they are non-metals and do not conduct electricity.
Q29. The gas bubbles seen at electrodes when current passes through water containing a little acid are of:
When electric current passes through acidified water, electrolysis occurs, producing oxygen gas at the anode and hydrogen gas at the cathode. This is the decomposition of water into its elements. Chlorine, nitrogen, and only oxygen are not produced in this process.
Q30. Which of the following liquids will make a bulb glow brightest?
Dilute hydrochloric acid is a strong electrolyte and contains many ions, making it a good conductor. The bulb will glow brightest with it. Distilled water, sugar solution, and alcohol are poor conductors and will not make the bulb glow.
Q31. An LED is preferred over a bulb in a conductivity tester because:
An LED is preferred in a conductivity tester because it glows even with a weak current. This makes it sensitive enough to detect weak conductivity in liquids. A bulb requires a stronger current to glow. LEDs are also more energy-efficient and durable.
Q32. The process of decomposition of a liquid by passing electric current is called:
Electrolysis is the process of decomposing a liquid (electrolyte) by passing electric current through it. This causes chemical reactions at the electrodes, splitting the compound into its elements. Electroplating is deposition of metal, galvanisation is zinc coating, and crystallisation is solid formation.
Q33. Which of the following is a good conductor of electricity?
Vinegar is a good conductor of electricity because it is an acid and contains ions. Rubber, plastic, and wood are insulators that do not conduct electricity. Conductivity in liquids depends on the presence of free ions.
Q34. In an LED, the light is produced because of:
In an LED, light is produced by the movement of electrons in a semiconductor material. When electrons recombine with holes in the semiconductor, energy is released as light. This is different from a bulb, which produces light by heating a filament.
Q35. Which of the following objects is often electroplated with gold?
Jewellery and watch straps are often electroplated with gold to give them an attractive and corrosion-resistant finish. Iron nails are galvanised with zinc, plastic pipes are not electroplated, and wooden doors are not metals. Gold plating is common in decorative items.
Q36. To test whether a liquid conducts electricity, the circuit must be:
To test whether a liquid conducts electricity, the circuit must be closed (complete). Current flows only in a complete circuit. An open or broken circuit would not allow current to flow, and a short circuit would bypass the liquid, giving a false reading.
Q37. Which of the following is NOT an electroplated object?
A wooden chair is NOT an electroplated object because wood is a non-conductor and cannot be electroplated. Tin cans, gold-plated ornaments, and chromium-plated taps are all examples of electroplated metal objects. Electroplating is done on metal surfaces.
Q38. The electrolyte used in electroplating copper on an iron object is:
Copper sulphate solution is used as the electrolyte when electroplating copper onto an iron object. The copper ions in the solution are deposited on the cathode (iron object) as copper metal. Zinc sulphate would plate zinc, and sodium chloride and distilled water are not used.
Q39. Pure water is a poor conductor because:
Pure water is a poor conductor because it has no free ions to carry electric current. Conductivity in liquids requires the presence of ions. Pure water is neutral and does not ionise significantly. When salts are dissolved, ions are released, and water becomes conductive.
Q40. The anode in electroplating is made of:
The anode in electroplating is made of the metal that is to be deposited on the object. As current flows, metal ions from the anode dissolve into the electrolyte and are deposited on the cathode (the object being plated). The cathode is the object being plated.
Q41. Which of the following statements is true about LEDs?
LEDs have polarity, meaning they have a positive (longer lead) and a negative (shorter lead) terminal. They will only glow when connected correctly in a circuit. LEDs glow even with weak current and require a battery or power source. The leads are of different lengths to indicate polarity.
Q42. A metal that is a very good conductor of electricity is:
Copper is a very good conductor of electricity and is widely used in electrical wiring. Sulphur, carbon, and silicon are not good conductors; carbon and silicon are semiconductors or poor conductors. Metals are generally good conductors due to their free electrons.
Q43. Electroplating is done to:
Electroplating is done to make objects resistant to corrosion (rusting) and to give them a decorative, shiny finish. It does not make objects magnetic, heavier, or softer. Electroplating deposits a thin layer of a metal like zinc, chromium, gold, or silver on the object.
Q44. When electric current passes through a conducting liquid, the ions move towards:
In a conducting liquid, positive ions (cations) move towards the cathode (negative electrode), and negative ions (anions) move towards the anode (positive electrode). This movement of ions constitutes the electric current in the liquid. Opposite charges attract.
Q45. Which of the following is a poor conductor of electricity?
Cooking oil is a poor conductor of electricity because it does not contain ions. Sea water, orange juice (acidic), and baking soda solution (basic) all contain ions and conduct electricity. Cooking oil is an insulator like other non-polar liquids.
Q46. In an electroplating setup, the electrolyte must be:
The electrolyte in electroplating must be a conducting liquid, typically a salt solution containing ions of the metal to be deposited. For example, copper sulphate solution is used for copper plating. Solids and gases do not allow ion movement, and distilled water is a poor conductor.
Q47. The chemical effect of electric current is used in:
Electroplating uses the chemical effect of electric current to deposit a metal layer on an object. Electric fans work on the magnetic effect, heaters on the heating effect, and electric bells on the magnetic effect. Chemical effects are used in electrolysis and electroplating.
Q48. Which of the following is an example of a good conducting liquid?
Salt water is a good conducting liquid because it contains dissolved ions. Honey, glycerine, and petrol are poor conductors as they do not contain free ions. Conductivity in liquids is due to the presence of ions that carry electric charge.
Q49. The object that is electroplated with tin is:
Food cans are electroplated with tin to prevent rusting and corrosion. Tin is non-toxic and prevents iron from reacting with food. Gold jewellery is plated with gold, iron nails are often galvanised with zinc, and copper wires are not typically electroplated.
Q50. If the LED does not glow when dipped in a liquid, the liquid is likely:
If the LED does not glow, the liquid is a poor conductor or insulator. Good conductors and electrolytes would allow current to flow and light the LED. Acids are also conductors. The lack of glow indicates that the liquid does not contain enough ions to conduct electricity.