Latest Posts

Boojho made an electromagnet by winding 50 turns of wire over an iron screw. Paheli also made an electromagnet by winding 100 turns over a similar iron screw. Which electromagnet will attract more pins? Give reason.

Answer: An electromagnet works on the principle of the magnetic effect of electric current. It is formed when a strong... View Article

Why do we cover plug pinholes which are within the reach of children with cellotape or a plastic cover when not in use?

Answer: When not in use, we cover plug pin holes within reach of children with cello tape or a plastic... View Article

Name two electric devices for each were (i) heating effect of current is used and (ii) magnetic effect of current is used.

Answer: The heating effect of electric current is the phenomenon when a steady current flows through conductor the energy liberated... View Article

Can we use the same fuse in a geyser and a television set? Explain.

Answer: An electric fuse is required for it acts as a safety device and it checks excessive current flow. The... View Article

Why is an electric fuse required in all electrical appliances?

Answer: An electric fuse is required for it acts as a safety device and it checks excessive current flow. The... View Article

Why are compact fluorescent lamps (CFLs) preferred over electric bulbs?

Answer: CFL is an energy-saving bulb that consumes much less energy than the conventional incandescent lamps. It is made of... View Article

Paheli does not have a night lamp in her room. She covered the bulb of her room with a towel in the night to get dim light. Has she taken the right step? Give one reason to justify your answer.

Answer: No, the Paheli’s action was not appropriate. Steps taken by Paheli are wrong as towel may get burned due... View Article

Unscramble the following words: (i) TBTAYER (ii) SFEU (iii) HTRCO (iv) HICWTS

Answer: (i) Battery A combination of two or more cells is called a battery. All batteries are made up of... View Article

Fill in the blanks: (i) Our body is a ________ of electricity. (ii) An electric cell produces electricity from the _ in it. (iii) In an electric circuit a fuse is a _ _ to prevent possible fire. (iv) A combination of two or more cells is called a _______.

Answer: (i) Our body is a conductor of electricity. Electrical conductor is defined as materials that allow electricity to flow... View Article

Name the device used these days in place of electric fuses in electrical circuits.

Answer: Miniature Circuit Breaker (MCB) is the device used these days in place of electric fuses in electrical circuits. Electric fuses... View Article

Which property of a conducting wire is utilised in making electric fuse?

Answer: The low melting point of the wire is utilized in making electric fuse. Conductor of electricity An electrical conductor... View Article

Which of the following precautions need not be taken while using electric gadgets/appliances/circuit? (a) We should never touch a lighted electric bulb connected to the mains. (b) We should never experiment with the electric supply from the mains or a generator or an inverter. (c) We should never use just any wire or strip of metal in place of a fuse. (d) We should never turn the switch in ON position.

Answer: (d) We should never turn the switch in ON position. To use electric gadgets/appliances/circuit switch should be turned on... View Article

When a switch is in OFF position, (i) circuit starting from the positive terminal of the cell stops at the switch. (ii) the circuit is open. (iii) no current flows through it. (iv) current flows after some time. Choose the combination of the correct answer from the following. (a) all are correct (b) (ii) and (iii) are correct (c) only (iv) is correct (d) only (i) and (ii) are correct

Answer: (b) (ii) and (iii) are correct When the switch is off, the circuit will be incomplete hence it is... View Article

Three bulbs A, B, C are connected in a circuit as shown in Figure. When the switch is ‘ON’ (a) bulb C will glow first. (b) bulb B and C will glow simultaneously and bulb A will glow after some time. (c) all the bulbs A, B and C will glow at the same time. (d) the bulbs will glow in the order A, B and C.

Answer: (c) all the bulbs A, B and C will glow at the same time. Because the three bulbs are... View Article

Choose the statement which is not correct in the case of an electric fuse. (a) Fuses are inserted in electric circuits of all buildings. (b) There is a maximum limit on the current which can safely flow through the electric circuits. (c) There is a minimum limit on the current which can safely flow in the electric circuits. (d) If a proper fuse is inserted in a circuit it will blow off if current exceeds the safe limit.

Answer: (c) There is a minimum limit on the current which can safely flow in the electric circuits. In case... View Article

When an electric current flows through a copper wire AB as shown in Figure the wire (a) deflects a magnetic needle placed near it. (b) becomes red hot. (c) gives an electric shock. (d) behaves like a fuse.

Answer: (a) deflects a magnetic needle placed near it. A current-carrying wire acts as a magnet with a magnetic field... View Article

Boojho goes to the football ground to play football. The distance-time graph of his journey from his home to the ground is given in the Figure (a) What does the graph between point B and C indicate about the motion of Boojho? (b) Is the motion between 0 to 4 minutes uniform or nonuniform? (c) What is his speed between 8 and 12 minutes of his journey?

Answer: (a) As time changes, the graph between points B and C is parallel to the x-axis, indicating that there... View Article

Distance between Bholu’s and Golu’s house is 9 km. Bholu has to attend Golu’s birthday party at 7 o’clock. He started from his home at 6 o’clock on his bicycle and covered a distance of 6 km in 40 minutes. At that point, he met Chintu and he spoke to him for 5 minutes and reached Golu’s birthday party at 7 o’clock. With what speed did he cover the second part of the journey? Calculate his average speed for the entire journey. The speed with which Bholu covered the second part of the journey

Answer: The speed with which Bholu covered the second part of the journey = Distance left to reach Golu’s house/... View Article

Given below as Figure is the distance-time graph of the motion an object. (i) What will be the position of the object at the 20s? (ii) What will be the distance travelled by the object in 12s? (iii) What is the average speed of the object?

Answer: (i) At 20 s, the object will be 8 m away from the starting point. (ii) In 12 s,... View Article

Plot a distance-time graph of the tip of the second hand of a clock by selecting 4 points on x-axis and y-axis respectively. The circumference of the circle traced by the second hand is 64 cm.

Answer: We take four points on a clock at 3, 6, 9, and 12 hours before drawing the graph. At... View Article

«
1
…
1,372
1,373
1,374
1,375
1,376
…
5,472
»