BAL BHARATI PUBLIC SCHOOL, PITAMPURA, DELHI-110034
CLASS-8
CHEMISTRY ASSIGNMENT
CHEMICAL EFFECTS OF CURRENT
Q1. What are good and bad conductors of electric current?
Ans. Good conductors of current: Those materials which allow electric current to pass through them are
called good conductors of current.
Example: Copper, iron etc.
Bad conductors of current: Those materials which do not allow electric current to pass through them are
called bad conductors of current.
Example: Plastics, wood etc.
Q2. What is the purpose of a tester?
Ans. The purpose of a tester is to check whether a material allows electric current to pass through it or
not.
Q3. Why do we use a battery instead of a cell while testing the conductivity of current through a liquid?
Ans. We use a battery as the current generated by the liquids is very weak which cannot be detected by
using a cell.
Q4. A tester was made to test the conductivity of salt solution. However the bulb of the tester did not
glow. What could be the possible reasons?
Ans.
a) The connections are loose.
b) The filament of the bulb is broken.
c) The battery is discharged.
Q5. Identify the following solutions as good or bad conductors of electricity:
a) Vinegar
Good conductor
b) Soap solution
Good conductor
c) Mustard oil
Bad conductor
d) Honey
Bad conductor
e) Petrol
Bad conductor
f) Sugar solution
Bad onductor
g) Copper sulphate solution
Good conductor
Q6. Why should not we join the two free ends of a tester when it is not in use?
Ans. We should not join the two free ends of a tester when it is not in use so as to avoid the wastage of
battery.
Q7. Suggest the possible alternatives to test the conductivity of a weakly conducting solution.
Ans. To test the conductivity of a weakly conducting solution:
a) We can replace the bulb of a tester with an LED.
b) We can use a magnetic compass.
Q8. Why does not pure water conduct electricity? How can we make it conducting?
Ans. Pure water does not conduct electricity because of the absence of charged particles called ions in it.
It can be made conducting by adding a salt, an acid or a base in it.
Q9.
a)
b)
Ans.
a)
b)
What is the full form of LED?
Why is it preferred over a bulb while making a tester?
Light emitting diode.
An LED is preferred as it can glow even when the current passing through a circuit is weak.
Q10. Why should not we touch the electrical equipment with wet hands?
Ans. We should not touch the electrical equipment with wet hands as tap water and human body are good
conductors of electricity, so we can get an electric shock.