Multiple Choice Questions........................
Question 1: An electric current can produce
(a) heating effect only.
(b) chemical effect only.
(c) magnetic effect only.
(d) chemical, heating, and magnetic effects.
Solution 1: (d) chemical, heating, and magnetic effects.
When an electric current travels through a conducting solution, it induces a chemical reaction. Electric current has a chemical effect on all this.
When a current of electricity passes through the bulb. Its filament heats up, and the bulb begins to glow. This is the electric current's heating effect.
A magnetic field is generated when an electric current is passed through a circuit. This is the electric current's magnetic effect.
They found that the bulb in the setup A glows more brightly as compared to that of the setup B. You would conclude that
(a) higher current is flowing through the circuit in setup A.
(b) higher current is flowing through the circuit in setup B.
(c) equal current is flowing through both the circuits.
(d) the current flowing through the circuits in the two setups cannot be compared in this manner.
Solution 2: (a) higher current is flowing through the circuit in setup A.
Since solution A is a better conductor of electricity than solution B, more current flows through the circuit in setup A.
Question 3: Boojho’s uncle has set up an electroplating factory near his village. He should dispose of the waste of the factory
(a) in the nearby river.
(b) in the nearby pond.
(c) in the nearby cornfield.
(d) according to the disposal guidelines of the local authority.
Solution 3: (d) according to the disposal guidelines of the local authority.
In the electroplating industry, waste disposal is a major concern because it pollutes water and releases a toxic chemical into bodies of water. As a consequence, it should be disposed of in compliance with local legislation.
Question 4: When an electric current is passed through a conducting solution, there is a change of colour of the solution. This indicates
(a) the chemical effect of current.
(b) the heating effect of current.
(c) the magnetic effect of current.
(d) the lightning effect of current.
Solution 4: (a) the chemical effect of current
A chemical reaction occurs when an electric current is used to conduct a solution. This results in a colour transition, which is due to the chemical influence of electric current.
Question 5: Which one of the following solutions will not conduct electricity?
(a) lemon juice
(b) vinegar
(c) tap water
(d) vegetable oil
Solution 5: (d) vegetable oil
Since vegetable oil is devoid of ions, it is unable to conduct electricity.
Question 6: Which of the following metals is used in electroplating to make objects appear shining?
(a) iron
(b) copper
(c) chromium
(d) aluminium
Solution 6: (c) chromium
Since chromium has a reflective quality and is scratch resistant, it is used in electroplating to give objects a gleaming appearance.
Question 7:
Which of the following solutions will not make the bulb in glow in figure given below?
(a) sodium chlorides
(b) copper sulphate
(c) silver nitrate
(d) sugar solution in distilled water
Solution 7: (d) sugar solution in diluted water
Very Short Answer Questions...................
Question 8: Fill in the blanks:
(a) The object to be electroplated is taken as ____________ electrode.
(b) One of the most common applications of chemical effect of electric current is ______________.
(c) Small amount of a mineral salt present naturally in water makes it a______________ of electricity.
(d) Electroplating of ______________ is done on objects like water taps and cycle bell to give them a shiny appearance.
Solution 8:
(a) The object to be electroplated is taken as cathode electrode.
(b) One of the most common applications of chemical effect of electric current is electroplating.
(c) Small amount of a mineral salt present naturally in water makes it a conductor of electricity.
(d) Electroplating of Chromium is done on objects like water taps and cycle bell to give them a shiny appearance.
Question 9: Why is a layer of zinc-coated over iron?
Solution 9: Rust is formed when iron mixes with ambient air. Zinc is applied to the iron to keep it from rusting.
Question 10: Will the solution of sugar in distilled water conduct electricity?
Solution 10: The sugar solution is neither acidic nor basic, and it is unable to ionise and conduct electricity.
Question 11: Name the effect of current responsible for the glow of the bulb in an electric circuit.
Solution 11: Heating effect of electric current is responsible for the glowing of the bulb in an electric circuit.
Short Answer Questions...................
Solution 12: When you add another cell, enough current flows through the bulb to make it glow.
Question 13: Paheli set up an experiment using liquid A in the beaker as shown in given figure. She observed that the bulb glows. Then she replaced the liquid A by another liquid B. This time the bulb did not glow. Boojho suggested replacing the bulb by an LED. They observed that the LED glows. Explain.
Solution 13: The current flowing through liquid B might be insufficient to light the bulb, but it was sufficient to light the LED.
Question 14: Paheli wants to deposit silver on an iron spoon. She took a silver nitrate (AgNO3) solution in a beaker and set up a simple circuit for electroplating. Which terminal of the battery should the spoon be connected to? What material should the other electrode be made of?
Solution 14: The spoon should be wired to the battery's negative terminal. Silver can be used on the other electrode.
Question 15: Why is tin electroplated on iron to make cans used for storing food?
Solution 15: Tin is a more reactive metal than iron. Tin is coated over iron to prevent it from reacting with food while food is stored.
Question 16: Observe the given figure.
Which of these two circuits A or B shows the correct observation?
Solution 16: Diagram A is depicting the correct observation.
Question 17: Observe the following circuits carefully. In which circuit will the bulb glow. Write ‘Yes’ or ‘No’ in the blank space provided along each of the circuit given in Fig. 14.6.
Solution 17:
Long Answer Questions............................
Question 18: An electric current is passed through a conducting solution. List any three possible observations.
Solution 18: Three possible observations are
- The solution could become hot.
- Gas bubbles may form on the electrodes.
- There could be a change in the colour of the solution.
- Metal deposits can be seen on electrodes.
Question 19: In the circuit given in figure, Boojho observed that copper is deposited on the electrode connected to the negative terminal of the battery. Paheli tried to repeat the same experiment. But she could find only one copper plate. Therefore she took a carbon rod as a negative electrode. Will copper be still deposited on the carbon rod? Explain your answer.
Solution 19: Copper would be collected on the carbon rod from the copper sulphate solution. When an electric current is passed through a copper sulphate solution, it dissociates into copper and sulphate. Free copper is attracted to the electrode attached to the battery's negative terminal, i.e. the carbon rod, and deposits on it. Paheli can thus receive a copper coating on carbon rod.
Question 20: Observe the circuit given in figure.
Boojho set up this circuit for purification of copper. What will be the nature of –
(i) plate A (ii) plate B (iii) the solution? Explain the process of purification.
Solution 20:
i) Nature of plate A- Pure copper
ii) Nature of plate B- Impure copper
iii) Nature of the solution – Copper sulphate solution
Electroplating is the purification method used here.
Take copper sulphate and two copper plates that are approximately 10 cm x 4 cm in size. In a clean and dry beaker, pour 250 mL of distilled water. Two teaspoonfuls of copper sulphate should be dissolved in it. To make the copper sulphate solution more conductible, add a few drops of dilute sulphuric acid. Using sandpaper clean copper plates. After that, give them a good rinsing and let them air dry. Immerse the copper plates in copper sulphate solution after connecting them to the terminals of a battery.
Copper sulphate dissociates into copper and sulphate as an electric current is passed through the solution. The free copper is attracted to the electrode attached to the battery's negative terminal and deposited there.
Question 21: Observe the following circuit given in below figure.
Current does not flow in the circuit if there is a gap between the two wires. Does it indicate that air is a poor conductor of electricity? Does air never conduct electricity? Explain.
Solution 21: Air is a weak conductor of electricity in general. However, under such circumstances, such as when lightning strikes, air conducts electricity.
Question 22: Boojho made the circuit shown in below figure. He wanted to observe what happens when an electric current is passed through water. But he forgot to add a few drops of lemon juice to water. Will it make any difference to his observations? Explain.
Solution 22: If the water is purified, it will not conduct electricity without the addition of lemon juice, and no current will flow through the circuit. If the water is acidic, a weak current can flow through the circuits, causing bubbles to emerge on the negative electrode.
Question 23: Observing that the bulb does not glow in the circuit shown in given figure A, Boojho changed the circuit as shown in figure B. He observed deflection in the magnetic compass.
(i)What does the deflection in the magnetic compass indicate?
(ii) Why did the bulb not glow in figure A?
(iii) What would be the effect of an increase in the number of turns in the coil wound around the magnetic compass in figure B?
(iv) What will be observed if the number of cells is increased in the circuit shown in figure B?
Solution 23: (i) It shows that there is current in the circuit.
(ii) Since the current was insufficient to light the lamp, it did not shine.
(iii) The magnetic compass's deflection would increase.
(iv) The compass's deflection will continue to rise.
Question 24: You are provided with a magnetic compass, an empty matchbox, a battery of two cells and connecting wires. Using these objects how will you make a tester for testing an electric circuit? Draw the necessary circuit diagram and explain.
Solution 24:
As current flows through the circuit, the magnetic compass needle deflects. This is due to current's magnetic influence.