मराठी

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.

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प्रश्न

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.

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उत्तर

Paheli’s electromagnet will attract more pins as it has more number of turns of wire on it and thus a stronger electromagnet.

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  या प्रश्नात किंवा उत्तरात काही त्रुटी आहे का?
पाठ 14: Electric Current and Its Effects - SHORT ANSWER QUESTIONS [पृष्ठ ७८]

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एनसीईआरटी एक्झांप्लर Science [English] Class 7
पाठ 14 Electric Current and Its Effects
SHORT ANSWER QUESTIONS | Q 16. | पृष्ठ ७८

संबंधित प्रश्‍न

When the current is switched on through a wire, a compass needle kept nearby gets deflected from its north-south position. Explain.


Which way does the wire in the diagram below  tend to move? 

 


In the Activity shown below, how do we think the displacement of rod AB will be affected if

  1. current in rod AB is increased
  2. a stronger horse-shoe magnet is used
  3. length of the rod AB is increased?
  • Take a small aluminium rod AB (of about 5 cm). Using two connecting wires suspend it horizontally from a stand, as shown in Fig.
  • Place a strong horse-shoe magnet in such a way that the rod lies between the two poles with the magnetic field directed upwards. For this put the north pole of the magnet vertically below and south pole vertically above the aluminium rod (Fig.).
  • Connect the aluminium rod in series with a battery, a key and a rheostat.
  • Now pass a current through the aluminium rod from end B to end A.
  • What do you observe? It is observed that the rod is displaced towards the left. You will notice that the rod gets displaced.
  • Reverse the direction of current flowing through the rod and observe the direction of its displacement. It is now towards the right.
  • Why does the rod get displaced?


A current-carrying rod, AB, experiences a force perpendicular to its length and the magnetic field. Support for the magnet is not shown here, for simplicity.


(b) State whether the following statements are true or false:

(i) Magnetic poles exist in pairs.

(ii) Global warming is a desirable aspect of the intensified greenhouse effect.


Read the given passage and answer the following questions:

The home electrical connection consists of ‘live’, ‘neutral’ and ‘earth’ wires. The ‘live’ and the ‘neutral’ wires have potential difference of 220 V. The ‘earth’ is connected to ground. Due to a fault in the equipment or if the plastic coating on the ‘live’ and the ‘neutral’ wires gives a way the two wires come in contact with each other and a large current flows through it producing heat. If any inflammable material (such as wood, cloth, plastic, etc.) exists around that place it can catch fire. Therefore a fuse wire is used as a precautionary measure.

  1. Name the two wires having potential difference of 220 V.
  2. What is a short circuit?
  3. Write the function of a fuse.

Explain the magnetic field created around a straight current carrying conductor with the help of a diagram.


If the key in the given arrangement is taken out (the circuit is made open) and magnetic field lines are drawn over the horizontal plane ABCD, the lines are ____________.


What is that instrument which can detect the presence of electric current in a circuit?


Magnetic effect of current was discovered by ______.


A student was asked to perform an experiment to study the force on a current carrying conductor in a magnetic field. He took a small aluminium rod AB, a strong horse shoe magnet, some connecting wires, a battery and a switch and connected them as shown. He observed that on passing current, the rod gets displaced. On reversing the direction of current, the direction of displacement also gets reversed. On the basis of your understanding of this phenomenon, answer the following questions: 

  1. Why does the rod get displaced on passing current through it?
  2. State the rule that determines the direction of the force on the conductor AB.
    1. If the U-shaped magnet is held vertically and the aluminium rod is suspended horizontally with its end B towards due north, then on passing current through the rod from B to A as shown, in which direction will the rod be displaced?
    2. Name any two devices that use current carrying conductors and magnetic fields.

OR

Draw the pattern of magnetic field lines produced around a current carrying straight conductor held vertically on a horizontal cardboard. Indicate the direction of the field lines as well as the direction of current flowing through the conductor.


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