Lakhmir Singh and Manjit Kaur Science solution: Chemical Effects Of Electric Current Chapter 14. Here you get easy solutions of Lakhmir Singh and Manjit Kaur Science solution Chapter 14 . Here we give Chapter 14 all solution of Class 8. Its help you to complete your homework.
- Board – CBSE.
- Text Book – SCIENCE.
- Class – 8.
- Chapter – 14.
VERY SHORT ANSWER TYPE QUESTIONS Answers:
1) Some liquids can conduct electricity.
2) Two liquid which conduct electricity are water and lemon juice.
Two liquid which not conduct electricity are distilled water and oil alcohol.
4) Light Emitting Diodes.
5) Lemon juice is a good conductor of electricity.
6) Vinegar is a acetic acid solution so it’s a good electricity conduct.
7) Chemical effect.
8) Chemical effect.
9) a> Oxygen gas, b> Hydrogen gas.
11) Electric current should be pass.
15) Bathroom taps; bicycle handlebars.
17) Silver, Gold.
19) Bicycle handlebars, bicycle bells, wheel rims, LPG stoves, Bathroom parts.
20) Copper, Zinc.
21) Sodium, aluminum.
24) a>True, b> False.
25) a>Acid base, Salt, b>Low, c> Chemical, d> Oxygen, Hydrogen, e> electroplating, f>Negative.
SHORT ANSWER TYPE QUESTIONS Answers:
26) Liquids conduct electricity are:
- Lemon juice.
- Common salt solution.
- Sulphuric acid solution.
- Sea water
- Rain water
Liquid do not conduct electricity :
- Sugar solution
- Distilled water.
27) We should never operate an electric switch or touch any working electrical appliance with wet hands because the tap water present an wet hands is a conductor of electricity due to which it may conduct electric current current from the electric switch to our hands and give us electric shock.
28) We can use LED in testing the electrical conductivity of liquid in place of torch bulb for detecting week electrical current passing through a liquid. LED is semiconductor device which glows even when a very week current passes through it. There are two wires attach to LED. One lead is slightly longer than the other. While connecting LED in the circuit the longer is always connected to the positive terminal of the battery whereas the shorted lead is always connected to negative terminal of the battery.
29) a> Liquid effect of current
b> Magnetic effect of current.
30) If a compass surrounded by wound up electric wire of a circuit including a liquid in it show delection.
This because even a week electric current flowing through a wire produces a magnetic field around and these magnetic field of electric current acts on the magnetic needle of the compass and deflects it from its its usual North South direction.
31) Distilled water is a poor conductor because it does not contain any dissolved salts on it, but tap water contains some minerals that’s why tap water conducts some electricity.
32) A small amount of salt can be added to distilled water in small amounts to make it a good conductor of electricity.
Salt solution is a good conductor of electricity. When salt dissolved, distilled water can be good conductor of electricity.
33) Sea water is a good conductor of electricity. This is because sea water contains more amounts of various salts dissolved in it whereas drinking water (Tap water) contains small amount of various salt dissolved in it.
34) Because of the chromium plating, new bicycle have shining handlebar and wheel rims.
If these are accidently scratched, the shiny chromium plating comes off and the iron or steel surface beneath it get exposed.
35) No, it is not safe for the electrician to carry out electrical repairs outdoors during heavy downpour.
Rain water is said to be pure water. But, when rain water falls to the earth through the atmosphere it dissolves and acidic gas carbon di oxide from the air and forms a weak acid called Carbonic acid. Due to the presence of small amounts of acid, rain water becomes good conductor of electricity. That’s why it is’nt safe for electrician as because rain water being a conductor of electricity may cause electrocution of the electrician.
36) This is because even a weak electric current flowing through a wire produces a magnetic field around it and these magnetic field of electric current acts on the magnetic needle of the compass and deflects it from its usual north-south direction. So, if a compass surrounded by wound up electric wire of a circuit including a liquid in it shows deflection. It will mean that the liquid conducts electricity.
37) We will observe that the bubbles of gases are produced at the two carbon carbon electrodes. The formation of gas bubbles at the two carbon electrodes shows that a chemical change has taken place in water on passing electric current through it.
38) Pure water conduct a small amount of electricity.
We can make pure water to conduct electricity in the following ways-
(i) We can dissolve some common salt to make it a good conductor of electricity.
(ii) We can add a little of acid to make it a good conductor of electricity.
(ii) We can add a little of base to make it a good conductor of electricity.
39) They cut off electricity supply for the area to prevent electrocution.
40) a> Electroplating.
b> Negative terminal of the battery is connected to the iron object.
The name of the electrolyte is Copper sulphate solution.
41) a> The materials which allow electric current to pass through them easily are called good conductors of electricity.
b> The application of chemical effects are : Electroplating metals, Purification of metals.
c> The Chemical decomposition produced by passing an electric through a conducting liquid is called electrolysis.
42) The three substances are Acid, Bases and salts can produce a chemical effects
The filament in the bulb has resistance. The current flowing through the resistance of bulb causes the filament to dissipate energy in the form of heat and light. The filament is actually glowing white-hot because of the energy it is dissipating. This is how giving off light.
43) (a)The process of depositing a thin layer of a desired metal over a metal object with the help of electric current is called electroplating.
The purpose of electroplating is to protection against corrosion.
(b) For the shining appearance, Chromium metal make it suitable for electroplating.