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Unscramble the following words: HTRCO - Science

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Unscramble the following words:

HTRCO

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पाठ 14: Electric Current and Its Effects - VERY SHORT ANSWER QUESTIONS [पृष्ठ ७७]

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एनसीईआरटी एक्झांप्लर Science [English] Class 7
पाठ 14 Electric Current and Its Effects
VERY SHORT ANSWER QUESTIONS | Q 9. (iii) | पृष्ठ ७७

संबंधित प्रश्‍न

An electric bell has an electromagnet. 


Fill in the following blank with suitable words: 

The magnetic effect of a coil can be increased by increasing the number of ........... increasing the ........... or inserting an ........... core.


The direction of current flowing in the coil of an electromagnet at its two ends X and Y are as shown below:  

  

 What is the polarity of end X?

What is the polarity of end Y?   

Name and state the rule which you have used to determine the polarities. 


When the switch S is closed in the figure given below, the pointer of the galvanometer moves to the right.  

 

If S is kept closed, will the pointer:

(a) return to zero?
(b) stay over on the right?
(c) move to the left and stay there
(d) move to and fro until S is opened


The north pole of a long bar magnet was pushed slowly into a short solenoid connected to a galvanometer. The magnet was held stationary for a few seconds with the north pole in the middle of the solenoid and then withdrawn rapidly. The maximum deflection of the galvanometer was observed when the magnet was ______.


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.


Observe the following diagram and choose the correct alternative:


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 ____________.


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.


Sailors use ______ to find direction in order to navigate on the sea.


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