Chemical Effects of Electric Current - Class 8 - Science
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Back Questions - Chemical Effects of Electric Current | NCERT | Science | Class 8
Fill in the blanks.
(a) Most liquids that conduct electricity are solutions of, ______________ and ______________.
(b) The passage of an electric current through a solution causes ______________ effects.
(c) If you pass current through copper sulphate solution, copper gets deposited on the plate connected to the ______________ terminal of the battery.
(d) The process of depositing a layer of any desired metal on another material by means of electricity is called ______________ .
(a) Most liquids that conduct electricity are solutions of, acids, bases, and salts.
(b) The passage of an electric current through a solution causes chemical effects.
(c) If you pass current through copper sulphate solution, copper gets deposited on the plate connected to the negative terminal of the battery.
(d) The process of depositing a layer of any desired metal on another material by means of electricity is called electroplating.
When the free ends of a tester are dipped into a solution, the magnetic needle shows deflection. Can you explain the reason?
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Sign up nowName three liquids which, when tested in the manner shown in Fig.11.9, may cause the magnetic needle to deflect.
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Sign up nowThe bulb does not glow in the setup shown in Fig.11.10. List the possible reasons. Explain your answer
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Sign up nowA tester is used to check the conduction of electricity through two liquids, labelled A and B. It is found that the bulb of the tester glows brightly for liquid A while it glows very dimly for liquid B. You would conclude that
(i) liquid A is a better conductor than liquid B.
(ii) liquid B is a better conductor than liquid A.
(iii) both liquids are equally conducting.
(iv) conducting properties of liquid cannot be compared in this manner.
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Sign up nowDoes pure water conduct electricity? If not, what can we do to make it conducting?
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Sign up nowIn 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.
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Sign up nowA child staying in a coastal region tests the drinking water and also the seawater with his tester. He finds that the compass needle deflects more in the case of seawater. Can you explain the reason?
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Sign up nowIs it safe for the electrician to carry out electrical repairs outdoors during heavy downpour? Explain.
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Sign up nowPaheli had heard that rainwater is as good as distilled water. So she collected some rainwater in a clean glass tumbler and tested it using a tester. To her surprise she found that the compass needle showed deflection. What could be the reasons?
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Sign up nowPrepare a list of objects around you that are electroplated.
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Sign up nowThe process that you saw in Activity 11.7 is used for 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 sought to be transferred to the thin copper plate. Which electrode should be attached to the positive terminal of the battery and why?
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Sign up nowExtra Questions - Chemical Effects of Electric Current | NCERT | Science | Class 8
When electric current is passed through a bulb, the bulb gives light because of:
A) electric effect of current
B) heating effect of current
C) glowing effect of current
D) lighting effect of current
The correct answer is Option B: heating effect of current.
The reason a bulb emits light when electric current passes through it is primarily due to the heating effect of current. In bulbs, particularly incandescent bulbs, a special type of wire known as tungsten is used. When electric current flows through the tungsten filament, it experiences resistance, leading to the generation of heat. As the temperature of the tungsten wire increases, it glows and emits light. The glow and subsequent emission of light are direct results of the filament reaching a high temperature, which is achieved due to the heating effect of electrical current.
Which of the following is not an after effect of a current passing through a conducting liquid?
A. Color of the solution may change.
B. Temperature of the solution may increase.
C. Bubbles can be seen near the electrodes.
D. Electrolyte solidifies to form a concentrate.
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Sign up nowWhich effect of current is responsible for electrolysis of salt solution?
A) Magnetic effect of electric current
B) Heating effect of electric current
C) Chemical effect of electric current
D) All of these
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Sign up nowLong Questions - Chemical Effects of Electric Current | NCERT | Science | Class 8
Explain in detail what happens when an electrical circuit tester is used on a liquid that conducts electricity. Discuss the mechanisms by which the tester indicates whether or not the liquid allows the electric current to pass through, including the role of the bulb in the tester and how its glow or lack thereof represents the current’s strength.
When a liquid that conducts electricity is tested with an electrical circuit tester, the tester completes its circuit and allows electric current to pass through the liquid, thereby causing the bulb in the tester to glow. This suggests that the liquid is a good conductor of electricity. Conversely, if the liquid does not allow the electrical current to pass, the tester's circuit remains incomplete, and the bulb does not glow, indicating that the liquid is a poor conductor. However, there may be scenarios where even a conducting liquid will not make the bulb glow due to too weak of a current. This is because the bulb's glow is dependent on the heating effect generated by the strength of the electric current. If the current is weak the bulb's filament does not get heated sufficiently and it does not glow.
Describe the process of electroplating and discuss its range of applications in different industries. Highlight the advantages of electroplating, specifically discussing why certain metals are chosen for the process and how electroplating makes objects more durable, aesthetically pleasing, or cost-effective.
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Sign up nowShort Questions - Chemical Effects of Electric Current | NCERT | Science | Class 8
Why is it dangerous to touch an electrical appliance with wet hands?
It is dangerous to touch an electrical appliance with wet hands because water is a good conductor of electricity. Through water, electric current can pass more easily, resulting in electrical shock.
Which metals are considered good conductors of electricity?
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Sign up nowWhat is a common feature of most liquids that can conduct electricity?
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