Short Questions with answers
1. What is a good conductor of electricity?
Answer : A material that allows electric current to pass through it.
2. What is the use of a tester?
Answer : It checks whether a material conducts electricity.
3. Why does the bulb glow in a tester?
Answer : The bulb glows due to the heating effect of electric current.
4. What is distilled water’s conductivity?
Answer : Distilled water does not conduct electricity.
5. What is electroplating?
Answer : It is the process of coating a metal using electricity.
6. What does the passage of current through a solution cause?
Answer : It causes chemical effects like gas formation or color change.
7. Why is salt water a good conductor?
Answer : Salt water contains ions that conduct electricity.
8. What happens when copper sulphate solution conducts electricity?
Answer : Copper deposits on the negative electrode.
9. What is an LED?
Answer : An LED is a Light Emitting Diode used in testers for weak currents.
10. What is the role of electrodes in electrolysis?
Answer : Electrodes transfer current into a solution during electrolysis.
11. What effect does electric current have on a compass needle?
Answer : It causes the needle to deflect.
12. What happens to metals during electroplating?
Answer : A thin layer of one metal gets deposited onto another.
13. What is a poor conductor of electricity?
Answer : A material that resists the flow of electric current.
14. Why does rainwater conduct electricity but not distilled water?
Answer : Rainwater contains dissolved salts and minerals.
15. What happens to electrodes in electroplating?
Answer : Metal transfers from one electrode to another.
16. What do you observe during electrolysis of water?
Answer : Bubbles of hydrogen and oxygen are formed.
17. Which electrode is connected to the negative terminal in electroplating?
Answer : The object to be electroplated.
18. What is the role of dilute acids in electroplating?
Answer : They enhance the conductivity of the solution.
19. Name one application of electroplating.
Answer : Coating car parts with chromium.
20. What is the role of salt in distilled water during electrolysis?
Answer : It makes the solution conductive.
Medium Questions with answers
1. Why does the bulb in a tester sometimes not glow even if the liquid conducts electricity?
Answer : If the liquid conducts poorly, the current may be too weak to heat the bulb’s filament. In such cases, the circuit is complete, but the bulb doesn’t glow.
2. How can distilled water be made a good conductor?
Answer : Distilled water can conduct electricity if impurities like salt, acids, or bases are added. These substances release ions, enabling conductivity.
3. What happens to a potato when a tester is inserted into it?
Answer : The potato shows a greenish-blue spot near the positive terminal, indicating a chemical effect of current. This reaction can help identify the positive terminal.
4. Why do firemen shut off electricity during firefighting?
Answer : Water conducts electricity, and if live wires are present, there’s a risk of electrocution. Turning off electricity ensures safety.
5. Why do some liquids conduct electricity while others do not?
Answer : Liquids that contain ions (e.g., salt water or acids) conduct electricity, while pure liquids like distilled water lack free ions and do not conduct.
6. What is the role of electrodes in electroplating?
Answer : Electrodes carry current through the solution, enabling the deposition of metal on the cathode (negative electrode). The anode provides metal ions to the solution.
7. Why is tap water a better conductor than distilled water?
Answer : Tap water contains dissolved salts and minerals, which release ions, making it conductive. Distilled water lacks these ions.
8. What is the significance of using LED instead of a bulb in a tester?
Answer : An LED can detect weak currents more effectively than a bulb. It requires less current to glow, making it ideal for low-conductivity liquids.
9. What chemical change occurs in water when current flows through it?
Answer : Water decomposes into hydrogen and oxygen gases, which are released at the electrodes. This is an example of electrolysis.
10. Why are metals used for electroplating?
Answer : Metals like chromium or gold are used for their desirable properties, such as corrosion resistance or a shiny appearance, which are transferred to other objects.
Long Questions with answers
1. What are the chemical effects of electric current on a solution?
Answer : When electric current passes through a solution, it may cause chemical changes like the formation of gas bubbles, deposition of metal, or changes in solution color. The type of change depends on the electrodes and the solution used.
2. Explain why pure water does not conduct electricity but saltwater does.
Answer : Pure water lacks free ions, so it cannot conduct electricity. However, when salt is dissolved in it, the solution contains positive and negative ions, which allow the flow of current. This makes saltwater a good conductor.
3. How does the process of electroplating work?
Answer : Electroplating involves passing current through a solution with the object to be plated as the negative electrode. Metal ions from the positive electrode deposit onto the object, creating a thin layer of the desired metal.
4. How can we use an LED to detect weak currents?
Answer : An LED glows even with weak currents, unlike traditional bulbs that need more current to heat the filament. This makes LEDs suitable for testing liquids with low conductivity.
5. What safety precautions should be taken while working with electricity and liquids?
Answer : Always use a low-voltage source like a battery, avoid touching live wires with wet hands, and ensure you’re not standing on a wet surface. These steps prevent electric shocks and accidents.
6. What happens during the electrolysis of copper sulphate solution?
Answer : When current flows through copper sulphate solution, copper ions from the solution deposit on the negative electrode. Simultaneously, copper from the positive electrode dissolves into the solution to maintain balance.
7. What is the role of electrodes in the chemical effects of electric current?
Answer : Electrodes conduct current into the solution, causing chemical reactions. The positive electrode releases metal ions into the solution, while the negative electrode attracts ions, leading to gas bubbles, metal deposition, or other changes.
8. Why does the compass needle deflect when a tester detects a conductor?
Answer : Electric current flowing through the tester creates a magnetic field around the wire. This magnetic effect causes the compass needle to deflect, indicating the presence of current.
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