Chemical effects of electric current Worksheet-3

Chemical effects of electric current Worksheet-3

 

  1. When the free ends of a tester are dipped into a solution the magnetic needle shows deflection. Can you explain the reason?

 

  1. The bulb does not glow in the set up shown in Figure. List the possible reasons. Explain your answer.

 

  1. Does pure water conduct electricity? If not what can we do to make it conducting?

 

  1. In case of a fire, before the firemen use the water hoses, they shut off the main electrical supply for the area. Explain why they do this.

 

  1. A child staying in the coastal region tests the drinking water and also the sea water with his tester. He finds that the compass needle deflects more in the case of sea water. Can you explain the reason?

 

  1. Is it safe for the electrician to carry out electrical repairs outdoors during heavy down­pour? Explain.

 

  1. Aaha collected some rain water in a clean glass tumbler and tested it using a tester. She found that the compass needle showed deflection. What could be the reasons?

 

  1. Prepare a list of objects around you that are electroplated.

 

  1. In purification of copper, a thin plate of pure copper and a thick rod of impure copper are used as electrodes. Copper from impure rod is to be transferred to the thin copper plate. Which electrode should be attached to the positive terminal of the battery and why?

 

  1. What are good conductors?

 

Answer:

  1. The magnetic needle shows deflection when circuit is complete. The deflection of magnetic needle shows that the solution is a good conductor.

 

  1. (i) The connections of the circuit may be loose.

(ii) Bulb may be fused.

(iii) Cells may be used up.

(iv) The liquid may be poor conductor.

 

  1. Pure water can be made conducting by dissolving salt in it.

 

  1. The water used in water hoses is good conductor of electricity. Firemen shut off the main electrical supply, because if the supply of electricity continues there is a high risk of electrocution due to water.

 

  1. Sea water contains more amount of salt than drinking water. So the sea water is a better conductor of electricity. This the reason that the compass needle deflects more in case of sea water.

 

  1. No, because during heavy downpour there is a higher risk of electrocution.

 

  1. Rain water is like a distilled water but some impurities are mixed in it from the atmosphere. These impurities make the rain water conducting. This could be the reason for the deflection of compass needle.

 

  1. Pots and artifacts of metal, taps in bathrooms and kitchen, jewelry  and ornaments, handle bar of cycles and motor cycles, gas burner, bottom of cooking utensils, handles of doors, tin cans  etc.

 

  1. The rod of impure copper plate should be connected to the positive terminal of the battery. Because when electric current is passed through the copper sulphate solution it is dissociated into copper and sulphate. The free copper drawn to the negative terminal of the battery and get deposited on it. On the other hand the loss of copper from the solution would be regained from the impure copper rod which is connected to the positive terminal of the battery.

 

  1. The materials which allow electric current to pass through them are called good conductors of the electricity.