{"id":24458,"date":"2021-06-17T18:17:03","date_gmt":"2021-06-17T12:47:03","guid":{"rendered":"https:\/\/mcq-questions.com\/?p=24458"},"modified":"2022-03-02T10:38:19","modified_gmt":"2022-03-02T05:08:19","slug":"ncert-solutions-for-class-7-science-chapter-14","status":"publish","type":"post","link":"https:\/\/mcq-questions.com\/ncert-solutions-for-class-7-science-chapter-14\/","title":{"rendered":"NCERT Solutions for Class 7 Science Chapter 14 Electric Current and its Effects"},"content":{"rendered":"

These NCERT Solutions for Class 7 Science<\/a> Chapter 14 Electric Current and its Effects Questions and Answers are prepared by our highly skilled subject experts to help students while preparing for their exams.<\/p>\n

Electric Current and its Effects NCERT Solutions for Class 7 Science Chapter 14<\/h2>\n

Class 7 Science Chapter 14 Electric Current and its Effects Textbook Exercise Questions and Answers<\/h3>\n

Question 1.
\nDraw in your notebook the symbols to represent the following components of electrical circuits: connecting wires, switch in the \u2018OFF\u2019 position, bulb, cell, switch in the \u2018ON\u2019 position, and battery.
\nAnswer:
\n\"NCERT<\/p>\n

Question 2.
\nDraw the circuit diagram to represent the circuit shown in figure given below.
\n\"NCERT
\nAnswer:
\n\"NCERT<\/p>\n

Question 3.
\nThe given figure shows four cells fixed on a board. Draw lines to indicate how you will connect their terminals with wires to make a battery of four cells.
\n\"NCERT
\nAnswer:
\n\"NCERT<\/p>\n

Question 4.
\nThe bulb in the circuit shown in given figure does not glow. Can you identify the problem? Make necessary changes in the circuit to make the bulb glow.
\n\"NCERT
\nAnswer:
\nThe positive terminals of both the cells are together and that is why the bulb is not glowing. The cells should be kept in a way that the positive terminal of one cell is near the negative terminal of another cell, to make the bulb glow.
\n\"NCERT<\/p>\n

Question 5.
\nName any two effects of electric current.
\nAnswer:
\nThe effects of electric current are:<\/p>\n

    \n
  1. Heating effect<\/li>\n
  2. Magnetic effect<\/li>\n<\/ol>\n

    \"NCERT<\/p>\n

    Question 6.
    \nWhen the current is switched on through a wire, a compass needle kept nearby gets deflected from its north-south position. Explain.
    \nAnswer:
    \nThe needle gets deflected when it is kept near a current carrying wire due to the magnetic effect of the current. The needle of the compass is made up of a thin magnet and when it comes in contact with the current carrying wire, which also acts like a magnet, then the like poles repel each other and opposite poles attract each other. Therefore the needle gets deflected.<\/p>\n

    Question 7.
    \nWill the compass needle show deflection when the switch in the circuit shown below is closed?
    \n\"NCERT
    \nAnswer:
    \nThe compass needle does not get deflected as there is no battery or any source of current.<\/p>\n

    Question 8.
    \nFill in the blanks:
    \na. Longer line in the symbol for a cell represents it\u2019s ………………… terminal.
    \nb. The combination of two or more cells is called a …………………
    \nc. When current is switched \u2018on\u2019 in a room heater, it …………………
    \nd. The safety device based on the heating effect of electric current is called a …………………
    \nAnswer:
    \na. positive,
    \nb. battery,
    \nc. becomes red hot and emits heat
    \nd. fuse<\/p>\n

    Question 9.
    \nMark \u2018T\u2019 if the statement is true and \u2018F\u2019 if it is false:
    \na. To make a battery of two cells, the negative terminal of one cell is connected to the negative terminal of the other cell. (T\/F)
    \nb. When the electric current through the fuse exceeds a certain limit, the fuse wire melts and breaks. (T\/F)
    \nc. An electromagnet does not attract a piece of iron. (T\/F)
    \nd. An electric bell has an electromagnet. (T\/F)
    \nAnswer:
    \na. F,
    \nb. T,
    \nc. F,
    \nd. T<\/p>\n

    Question 10.
    \nDo you think an electromagnet can be used for separating plastic bags from a garbage heap? Explain.
    \nAnswer:
    \nElectromagnets can only attract magnetic materials. Plastic bag is a non-magnetic material and will not be attracted by an electromagnet. Hence, an electromagnet cannot be used for separating plastic bags from a garbage heap.<\/p>\n

    Question 11.
    \nAn electrician is carrying out some repairs in your house. He wants to replace a fuse by a piece of wire. Would you agree? Give reasons for your response.
    \nAnswer:
    \nNo, we would not agree to replace the fuse by a wire. Wires in the fuses are of specific melting points. So we should always use ISI marked fuses in our houses to prevent short circuits.<\/p>\n

    \"NCERT<\/p>\n

    Question 12.
    \nZubeda made an electric circuit using a cell holder shown in the given figure, a switch and a bulb. When she put the switch in the \u2018ON\u2019 position, the bulb did not glow. Help Zubeda in identifying the possible defects in the circuit.
    \n\"NCERT
    \nAnswer:
    \nThe cells should be connected properly. The positive terminal of one cell should be in series with the negative terminal of the other cell. The switch should be closed properly and a bulb which is fused should not be used. Then, the bulb will certainly glow.<\/p>\n

    Question 13.
    \nIn the circuit shown in the figure given below
    \n\"NCERT
    \na. Would any of the bulbs glow when the switch is in the \u2018OFF\u2019 position?
    \nb. What will be the order in which the bulbs A, B and C will glow when the switch is moved to the \u2018ON\u2019 position?
    \nAnswer:
    \na. No, when the switch is in \u2018OFF\u2019 position, the current does not flow through the circuit. Hence, none of the bulbs will glow,
    \nb. Bulbs will glow simultaneously. When the switch is moved to the \u2018ON\u2019 position, then all the bulbs will glow at once. This is because they all are connected to the same battery and switch.<\/p>\n

    NCERT Extended Learning Activities and Projects<\/span><\/p>\n

    Question 1.
    \nSet up the circuit shown in fig 14.17 (of NCERT textbook) again. Move the key to \u2018ON\u2019 position and watch carefully in which direction the compass needle gets deflected. Switch \u2018OFF\u2019 the current. Now keeping rest of the circuit intact, reverse the connections at the terminals of the cell. Again switch \u2018ON\u2019 the current. Note the direction in which the needle gets deflected. Think of an explanation.
    \nHint:
    \nThe direction of magnetic poles get reversed in a conductor, when the direction of current is reversed. Hence, the needle will show deflection in opposite direction in the second case.<\/p>\n

    Question 2.
    \nMake four electromagnets with 20, 40, 60 and 80 turns. Connect them one by one to a battery of 2 cells. Bring the electromagnet near a box of pins. Count the number of pins attracted by it. Compare the strengths of the electromagnets.
    \nHint:
    \nThe electromagnet with 80 turns will attract the maximum number of pins, followed by that of 60 turns, then 40 turns and finally 20 turns which will attract the least number of pins. This is because the strength of an electromagnet increases by increasing the number of turns in the coil.<\/p>\n

    \"NCERT<\/p>\n

    Question 3.
    \nUsing an electromagnet, you can make a working model of a railway signal as shown in figure given below.
    \n\"NCERT
    \nHint:
    \nTo make a model railway signal, you will need an iron nail, a thread, two pieces of plywood, a paper clip, a battery, a pencil and a length of copper wire. Fix the two pieces of plywood to each other. They . should be perpendicular to each other. Tie the nail through the thread and fix the thread to the vertical plyboard. Take a card and cut out a signal arm and fix it to the upper end of the jaw with the help of paper clip. Next, take the pencil and wind some copper wire around it, making a hollow coil. There should be extra copper wire at both the ends. Place the coil on the horizontal plywood and connect it to the battery. Insert an iron nail inside the coil loosely. Taking another drawing pin and a paper clip, create a circuit. When you complete the circuit, the nail will be attracted inwards into the coil. This is because it creates a magnetic field. You will find the signal arm moving up and down lifting the signal.<\/p>\n

    Question 4.
    \nVisit an electric shop. Request a mechanic to show you the various types of fuses and MCB and to explain how they work.
    \nHint:
    \nDo it yourself.<\/p>\n

    Activity 1<\/span><\/p>\n

    Objective: To demonstrate the heating effect of electric current.
    \nMaterials Required: Electric cell (1.5 volts), small torch bulb, switch, connecting wires with the insulation removed from its ends and adhesive tape.
    \nProcedure:<\/p>\n