PPT - Chemical Effects of Electric Current Class 7 Notes | EduRev

Science Class 7

Class 7 : PPT - Chemical Effects of Electric Current Class 7 Notes | EduRev

 Page 1


CHAPTER - 14 
 
CHEMICAL EFFECTS OF ELECTRIC 
CURRENT 
Page 2


CHAPTER - 14 
 
CHEMICAL EFFECTS OF ELECTRIC 
CURRENT 
1) Conduction tester :- 
      A conduction tester is a device used to determine whether a 
substance is a good or poor conductor of electricity. 
a) Conduction tester using a torch bulb :-   
     A simple conduction tester has an electric cell and a torch bulb. One 
terminal of the cell is connected to one terminal of the bulb by a wire. 
The other terminal of the cell and bulb have wires which can be brought 
in contact with materials to test whether they are good or poor 
conductors of electricity. 
    If the material is a good conductor, the bulb glows and if it is a poor 
conductor the bulb does not glow.  
Page 3


CHAPTER - 14 
 
CHEMICAL EFFECTS OF ELECTRIC 
CURRENT 
1) Conduction tester :- 
      A conduction tester is a device used to determine whether a 
substance is a good or poor conductor of electricity. 
a) Conduction tester using a torch bulb :-   
     A simple conduction tester has an electric cell and a torch bulb. One 
terminal of the cell is connected to one terminal of the bulb by a wire. 
The other terminal of the cell and bulb have wires which can be brought 
in contact with materials to test whether they are good or poor 
conductors of electricity. 
    If the material is a good conductor, the bulb glows and if it is a poor 
conductor the bulb does not glow.  
b) Conduction tester using LED :- 
    Sometimes the current flowing through the circuit may 
be too weak and the filament of the bulb may not get 
sufficiently heated to make it glow. Then instead of a torch 
bulb an LED can be used in the circuit. LED glows even 
when a weak current flows in the circuit.  
Page 4


CHAPTER - 14 
 
CHEMICAL EFFECTS OF ELECTRIC 
CURRENT 
1) Conduction tester :- 
      A conduction tester is a device used to determine whether a 
substance is a good or poor conductor of electricity. 
a) Conduction tester using a torch bulb :-   
     A simple conduction tester has an electric cell and a torch bulb. One 
terminal of the cell is connected to one terminal of the bulb by a wire. 
The other terminal of the cell and bulb have wires which can be brought 
in contact with materials to test whether they are good or poor 
conductors of electricity. 
    If the material is a good conductor, the bulb glows and if it is a poor 
conductor the bulb does not glow.  
b) Conduction tester using LED :- 
    Sometimes the current flowing through the circuit may 
be too weak and the filament of the bulb may not get 
sufficiently heated to make it glow. Then instead of a torch 
bulb an LED can be used in the circuit. LED glows even 
when a weak current flows in the circuit.  
c) Conduction tester using a magnetic compass :- 
   If a magnetic compass is kept near a wire and current 
flows through the wire, the magnetic needle gets deflected. 
So we can use a magnetic compass instead of a torch bulb 
or LED in the circuit. The  magnetic needle gets deflected 
even if a weak current flows in the circuit. 
Page 5


CHAPTER - 14 
 
CHEMICAL EFFECTS OF ELECTRIC 
CURRENT 
1) Conduction tester :- 
      A conduction tester is a device used to determine whether a 
substance is a good or poor conductor of electricity. 
a) Conduction tester using a torch bulb :-   
     A simple conduction tester has an electric cell and a torch bulb. One 
terminal of the cell is connected to one terminal of the bulb by a wire. 
The other terminal of the cell and bulb have wires which can be brought 
in contact with materials to test whether they are good or poor 
conductors of electricity. 
    If the material is a good conductor, the bulb glows and if it is a poor 
conductor the bulb does not glow.  
b) Conduction tester using LED :- 
    Sometimes the current flowing through the circuit may 
be too weak and the filament of the bulb may not get 
sufficiently heated to make it glow. Then instead of a torch 
bulb an LED can be used in the circuit. LED glows even 
when a weak current flows in the circuit.  
c) Conduction tester using a magnetic compass :- 
   If a magnetic compass is kept near a wire and current 
flows through the wire, the magnetic needle gets deflected. 
So we can use a magnetic compass instead of a torch bulb 
or LED in the circuit. The  magnetic needle gets deflected 
even if a weak current flows in the circuit. 
2) Electrical conductivity of solids :- 
    Some solids are good conductors of electricity. 
    Eg :- copper, steel, iron, aluminium etc. 
    Some solids are poor conductors of electricity. 
    Eg :- wood, plastic, rubber, glass etc. 
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