CBSE Class 8 Science Chapter 11 Short Answer Questions
Question 1. Boojho made the circuit as shown in the figure. He wanted to observe what happens when an electric current is passed through water, but he forgot to add a few drops of lemon juice to the water. Will it make any difference to his observations? Explain
Answer: Adding few drops of lemon juice in water will increase the conductivity of the solution. The current will flow in both the cases but adding of lemon juice makes it easy for the current to flow.
” CBSE Class 8 Science Chapter 11 Question and Answers “
Question 2. Observe the following circuit given in the figure.
” Chemical effects of electric current Class 8 “
No current does not flows in the circuit if there is a gap between the two wires. Does It Indicate that air is a poor conductor of electricity? Does air never conduct electricity? Explain.
Answer: Yes, current is not flowing through the air gap between the wires, which means that air is a poor conductor of electricity.
Air conducts electricity only when there is a great voltage or when there is some moisture in the air.
Read And Learn More CBSE Class 8 Science Short Answer Questions
Question 3. Boojho made the circuit given and observed that the bulb did not glow. On Paholl’s suggestion, I added one more cell in the circuit. The bulb now glows. Explain.
” Conductivity of liquids Class 8 “
Answer: Initially, the bulb was not glowing because the voltage required to make the bulb glow was not sufficient. When the voltage increases more than a particular value, the bulb starts glowing because it gets sufficient energy to heat its filament.
Question 4. Paheli setup an experiment using liquid A in the beaker as shown in figure. She observed that the bulb glows. Then, she replaced the liquid A by another liquid B. This time the bulb did not glow. Boojho suggested replacing the bulb by an LED. They observed that the LED glows. Explain.
Answer: Liquid A is a good conductor of electricity, and it allows the maximum current to pass through it, which is sufficient to glow the bulb.
But when it is replaced by another liquid B, the bulb does not glow because liquid B is not a good conductor of electricity. But the small current that is passing through B is sufficient to glow a low-voltage LED, so it glows.
” Electroplating process Class 8 “
Question 5. Last Monday, Ankush woke up late in the morning. So, he saw the time and suddenly realised that he had been late for an interview, which he was supposed to give after reaching the venue by the right time. Immediately, he turned ON the geyser, but it did not work. He got more tense, then he used an electric iron rod through which he could get some boiled water for his bath.
There was an earthing problem in the switchboard, which he was unaware of. He was barefoot and was just about to switch ON the electric iron rod, but at the same time, he was stopped from doing so by one of his roommates living with him. It could be dangerous for Ankush. Explain briefly what could have happened with Ankush. If he switched ON the electric iron rod (without wearing any slippers on his feet). Mention the values shown by Ankush’s friend.
Answer: If Ankush switched ON the electric iron rod and (without wearing any footwear), then he could have met with some accident, either in the form of electrical sparking or a short circuit of the switchboard.
Ankush’s friend seems to be very intelligent and very much concerned for Ankush as well.
” Lemon juice and vinegar conductivity “
” Magnetic needle deflection experiment “
Question 6. Observe the following circuits. In which circuit will the bulb glow? Write ‘Yes’ or ‘ No’ in the blank space provided along with each of the circuits given in the figure.
Answer:
- No
- Yes
- No
- Yes
” Bulb glowing in circuits “
Question 7. Name of three liquids which, when tested in the manner shown in the figure below, may cause the magnetic needle to deflect.
” Distilled water and salt solution “
Answer: The three liquids are as follows
- Tapwater
- HC1 or hydrochloric acid
- Sodium hydroxide
Question 8. The bulb does not glow in the setup shown in the figure below. List the possible reasons. Explain your answer
Answer: The possible reasons are as follows
- The current is not produced by the given liquid, and hence, the bulb does not glow.
- Connections are loose.
- The bulb is fused.
- Cells are used up.
” CBSE Class 8 Science question and answers “
Question 9. A tester is used to check the conduction of electricity through two liquids, labelled A and B. It is found that the bulb of the tester glows brightly for liquid A, while it glows very dimly for liquid B. You would conclude that
- Liquid A is a better liquid than Liquid II
- Liquid in a heller liquid A
- Both liquids are equally conducting
- Conducting properties of liquid annuli are compared in this manner
Answer: We conclude that liquid A is a better conductor than liquid II
Question 10. Does pure water conduct electricity? If not, what can we do to make it conducive?
Answer: No, pure water does not conduct electricity because it has no dissolved salt in it.
Hence, pure water can be made conducting by dissolving salt in it.