Aparna heated a bi-metallic strip made of two different types of metals for some time.

After heating it, she observed that the metallic strip curved as shown in the figure. Which of the following would best explain the conclusion derived by Aparna about the experiment she had done?

A student used the stroking method to magnetise a steel bar as shown in the figure.

If the steel bar was divided into parts I, II, III, and IV, which of these parts would be the north-pole?

Five lamps $L_1, L_2, L_3, L_4$ and $L_5$ and three different types of materials $M_1, M_2$ and $M_3$ are used in the circuit shown.

If $L_2, L_3$ and $L_4$ are the only lamps that light up, then which one of the following conclusions can be made?

Following are the precautions one must take in case a storm is accompanied by lightning.
(i) Do not take shelter under a tree.
(ii) Do not take shelter under an umbrella with a magnetic end.
(iii) Do not take shelter in open garages, storage sheds, etc.
(iv) Do not take shelter in a bus in the open field.
Which one of these is not correct?

A class $7$ science teacher arranged the following set of test tubes.

Which of the following observations is correct when these solutions were tested with different indicators?

Which of the following changes (i-vi) from the given list cannot be reversed?

(i) Breaking of an earthen pitcher.
(ii) Freezing of ice-cream.
(iii) Falling of bucket with water.
(iv) Filling of bucket with water.
(v) Rusting of a bicycle.
(vi) Digestion of food.

Which of the following statements is incorrect?