Question 1 :
A coating of zinc is provided to protect iron from corrosion and rust.

Question 2 :
<img style='object-fit:contain' src='https://teachmint.storage.googleapis.com/question_assets/cbse_ncert/61b1d050f59b460d7261f2c7.PNG' /> Current does not flow in the circuit if there is a gap between the two wires. Does air never conduct electricity?

Question 3 :
Boojho’s uncle has set up an electroplating factory near his village. He should dispose off the waste of the factory

Question 4 :
<img style='object-fit:contain' src='https://teachmint.storage.googleapis.com/question_assets/cbse_ncert/61b1d056f59b460d7261f2cf.PNG' /> In the image above, Boojho set up this circuit for purification of copper. What will be the nature of plate A?

Question 5 :
When electric current is passed through a conducting solution, there is a change of colour of the solution. This indicates

Question 8 :
<img style='object-fit:contain' src='https://teachmint.storage.googleapis.com/question_assets/cbse_ncert/61b1d054f59b460d7261f2cd.PNG' /> In the image above, Boojho set up this circuit for purification of copper. What will be the nature of plate B?

Question 9 :
<img style='object-fit:contain' src='https://teachmint.storage.googleapis.com/question_assets/cbse_ncert/61b1d050f59b460d7261f2c8.PNG' /> In the above image, observing that the bulb does not glow in the circuit shown in A, Boojho changed the circuit as shown in B. He observed deflection in the magnetic compass. Why did the bulb not glow in A?

Question 10 :
<img style='object-fit:contain' src='https://teachmint.storage.googleapis.com/question_assets/cbse_ncert/61b1d051f59b460d7261f2c9.PNG' /> In the above image, observing that the bulb does not glow in the circuit shown in A, Boojho changed the circuit as shown in B. He observed deflection in the magnetic compass. What will be observed if the number of cells are increased in the circuit shown in B?

Question 12 :
For human ears, the audible range is 20 Hz to 20,000 Hz. State true or false.

Question 13 :
Boojho saw a cracker burst at night at a distance from his house. He heard the sound of the cracker a little later after seeing the cracker burst. Give reason for the delay in hearing the sound.

Question 14 :
Which of the following voices is likely to have minimum frequency?

Question 17 :
Suppose a stick is struck against a frying pan in vacuum. Will we be able to hear the sound?

Question 18 :
The lower the frequency of vibration, the higher is the pitch. Is the given statement correct ?

Question 19 :
Loudness of sound is proportional to the square of the amplitude of the vibration producing the sound. State true or false.

Question 20 :
State True or False: Unwanted or unpleasant sound is termed as music.

Question 22 :
Lack of sleep, hypertension, anxiety and many more health disorders may be caused by ______________

Question 23 :
Presence of excessive noise in the surroundings may cause many health related problems. True or false ?

Question 24 :
<img style='object-fit:contain' src='https://teachmint.storage.googleapis.com/question_assets/cbse_ncert/61b1d0abf59b460d7261f333.jpeg' /> In the above figure an alarm bell is kept inside a vessel. A person standing close to it can distinctly hear the sound of alarm. Now if the air inside the vessel is removed completely how will the loudness of alarm get affected for the same person?

Question 25 :
Lightning can be seen the moment it occurs. Paheli observes lightning in her area. She hears the sound 5 s after she observed lightning. How far is she from the place where lightning occurs? (speed of sound = 330 m/s).