KSEEB Solutions for Class 7 Science Chapter 14 Electric Current and its Effects

Students can Download Chapter 14 Electric Current and its Effects Questions and Answers, Notes Pdf, KSEEB Solutions for Class 7 Science, Karnataka State Board Solutions help you to revise complete Syllabus and score more marks in your examinations.

Karnataka State Syllabus Class 7 Science Chapter 14 Electric Current and its Effects

Class 7 Science Electric Current and its Effects NCERT Textbook Questions and Answers

Question 1.
Draw in your notebook the symbols to represent the following components of electrical circuits: connecting wires, switch in the ‘OFF’ position, bulb, cell, switch in the ‘ON’ position, and battery
Answer:
KSEEB Solutions for Class 7 Science Chapter 14 Electric Current and its Effects 1

Question 2.
Draw the circuit diagram to represent the circuit shown in Fig.14.21.
Answer:
KSEEB Solutions for Class 7 Science Chapter 14 Electric Current and its Effects 2

Question 3.
Fig.14.22 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.
Answer:
KSEEB Solutions for Class 7 Science Chapter 14 Electric Current and its Effects 3 KSEEB Solutions for Class 7 Science Chapter 14 Electric Current and its Effects 4
To make a battery of cells, the positive terminal (+) of one cell always be connected to negative terminal (-) of another cell.

Question 4.
The bulb in the circuit shown in Fig.14.23 does not glow. Can you identify the problem? Make necessary changes in the circuit to make the bulb glow.
Answer:
KSEEB Solutions for Class 7 Science Chapter 14 Electric Current and its Effects 5
The positive terminal (+) of one cell always be connected to the negative terminal (-) of another cell. Here the two positive terminals are connected to each other. The correct arrangement is as follows.

Question 5.
Name any two effects of electric current.
Answer:
Heating effect of current: when an electric current passes through a wire, the wire gets heated. This is known as the heating effect of current. Which is used in many heating applications like electric heater, electric iron light bulb, etc.

Magnetic effect of current: when an electric current flows through a wire, it generates a magnetic field around it. this effect is called the magnetic effect of current. The magnetic effect of electric current has many applications like power lift, electric bell, electric fan etc.

Question 6.
When the current is switched on through a wire, a compass needle kept nearby gets deflected from its north-south position. Explain.
Answer:
When the current is switched on through a wire, the wire starts behaving as a magnet. Thus, when a compass needle is – placed near the wire, it gets influenced by the magnetic effect of electric current. Hence, the compass gets deflected from its North-South position.

Question 7.
Will the compass needle show deflection when the switch in the circuit shown in Fig. 14.24 is closed?
KSEEB Solutions for Class 7 Science Chapter 14 Electric Current and its Effects 55
Answer:
No, the compass needle will not show deflection even though the switch is closed, because there is no source of electric current. (Battery or cell) An electric cell or battery needs to be connected here. In the absence of an electric. current, there is no magnetic field produced by the wires, Hence there is no deflection.

Question 8.
Fill in the blanks:

  1. The longer line in the symbol for a cell represents its positive terminal.
  2. The combination of two or more cells is called a battery.
  3. When the current is switched ‘on’ in a room heater, it becomes hot.
  4. The safety device based on the heating effect of electric current is called a fuse.

Question 9.
Mark ‘T’ if the statement is true and ‘F’ if it is false:
Answer:
(a) 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)
Answer:
False

(b) When the electric current through the fuse exceeds a certain limit, the fuse wire melts and breaks. (T/F)
Answer:
True

(c) An electromagnet does not attract a piece of iron. (T/F)
Answer:
False

(d) An electric bell has an electromagnet. (T/F)
Answer:
True

Question 10.
Do you think an electromagnet can be used for separating plastic bags from a garbage heap? Explain.
Answer:
An electromagnet is just like as a bar magnet and it can attract iron pieces only. Plastic does not have any magnetic property, so electromagnet cannot be used to separate plastic bags from the garbage heaps.

Question 11.
An 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.
Answer:
No, because fuse is made of lead wire which has a very low melting point. A fuse wire melts quickly and breaks when large amount of current passes through the circuit. If the electrician replaces a fuse by a piece of ordinary wire (which has high melting point) it increases the risk of overheating due to flow of excessive current. This may lead to short circuit and fire.

Question 12.
Zubeda made an electric circuit using a cell holder shown in Fig. 14.4, a switch and a bulb. When she put the switch in the ‘ON’ position, the bulb did not glow. Help Zubeda in identifying the possible defects in the circuit.
Answer:
Possible reasons are the follows :

  1. The bulb may be fused or defective.
  2. Cells are not connected properly.
  3. There may be loose connections.
  4. The switch is not functioning well.
  5. The cells are dried up. i.e. the power of the cells has been exhausted.

Question 13.
In the circuit shown in fig.

KSEEB Solutions for Class 7 Science Chapter 14 Electric Current and its Effects 56
(i) Would any of the bulb glow when the switch is in the ‘OFF’ position?
None of the build will glow when the witch is in the ‘OFF’ position, since the electric circuit is not closed.
(ii) What will be the order in which the bulbs A, B and C will glow when switch is moved to the ‘ON’ position?
Answer:
When the switch is moved to the ‘ON’ position, the circuit is complete, and the electric current will flew immediately. All of the bulbs will glow instantly.

Class 7 Science Electric Current and its Effects Additional Important Questions and Answers

Question 1.
Write a table to show some electric circuit Components and their Symbols.
Answer:
KSEEB Solutions for Class 7 Science Chapter 14 Electric Current and its Effects 30

Question 2.
What is the battery? How do you arrange the cells in a battery?
Answer:
KSEEB Solutions for Class 7 Science Chapter 14 Electric Current and its Effects 31
Combination of two or more cells is called a battery. The cells should be arranged as the positive terminal of one cell is connected to the. the negative terminal of the next cell. It is shown in fig 14.3.
KSEEB Solutions for Class 7 Science Chapter 14 Electric Current and its Effects 32

Question 3.
What are the uses of the battery?
Answer:
Batteries are used in many devices such as torches, transistors, toys, TV remote controls, etc.

Question 4.
Where should we place the key or switch in the electric circuits?
Answer:
The key or Switch can be placed any¬where in the electric circuit.

Question 5.
When should we say that the circuit is closed?
Answer:
When the Switch is in the ON position, the circuit from the positive terminal of the battery to the negative terminal is connected then it is complete. The circuit is then said to be closed and the current flows throughout the circuit instantly.

Question 6.
When should we say the circuit is open?
Answer:
When the switch is in the OFF position, the circuit is incomplete. So it is said to be open. No current flows through any part of the circuit.

Question 7.
What is meant by the heating effect of electric current?
Answer:
Whenever the electric current flows through the wire, the wire gets hot. This is known as the heating effect of electric current.

Question 8.
what are factors does the heat produced in a wire depend on?
Answer:
The amount of heat produced in a wire depends on its material, length and thickness of the wire.

Question 9.
Name the devices which work on the heating effect of electric current.
Answer:
Electric iron, immersion heaters, hot plates, geysers, electric kettles, hair driers, etc, are worked on the heating effect of electric current.

Question 10.
How does the room heater work?
Answer:
The room heater or any heat appliances contain a coil of wire. This coil of wire is called an element. When these appliances are switched on after connecting to the electric circuit, their elements become red hot and give out heat.

Question 11.
What is a fuse? Why it is used?
Answer:
Wires made from some special materials melt quickly and break when a large amount of electric currents are passed through them. These wires are used for making electric fuses. In all buildings, fuses are inserted in all electrical circuits. There is a maximum limit on the current which can safely flow through a circuit. If by accident the current exceeds this safe limit, the wires may become overheated and may cause a fire. A fuse is a safety device which prevents damages to electrical circuits and fire.

Question 12.
Define miniature circuit breaker.
Answer:
Miniature circuit breakers are used in place of fuses. These are the switches which automatically turn off when the current in a circuit exceeds the safe limit.

Question 13.
What is meant by the magnetic effect of electric current?
Answer:
When an electric current passes through a wire, it behaves like a magnet. This is the magnetic effect of the electric current. If the electric current does not passes through, it loses its magnetic effect. These coils of wire are called electromagnets.

Question 14.
Who discovered the magnetic effect of electric current?
Answer:
Hans Christian odersted was the first person who noticed the deflection of the compass needle every time the current was passed
KSEEB Solutions for Class 7 Science Chapter 14 Electric Current and its Effects 33
through the wire.

Question 15.
How did an electric bill work?
Answer:
It consists of a coil of wire wound on an iron piece. The coil acts as an electromagnet. An iron strip with a hammer at one end is kept close to the electromagnet. There is a contact screw near the iron strip. When the iron strip is in contact with the screw, the current flows through the coil which becomes an electromagnet. Then it pulls the iron strip. In the process, the hammer at the end of the strip strikes the gong of the bell to produce a sound.

Question 16.
Who invented the electric bulb?
Answer:
Thomas – Alva – Edison invented the electric bulb. He was a remarkable inventor. He made some 1300 inventions including the electric bulb, gramophone, the motion picture camera, and the carbon transmitter.

Question 17.
Draw a neat circuit diagram of electric
Answer:
KSEEB Solutions for Class 7 Science Chapter 14 Electric Current and its Effects 34

Question 18.
What are the uses of electromagnets and magnets?
Answer:
Electromagnets are used in cranes, electric bells, loudspeakers, telephones, etc.