Electric Current and its Effects Class 7 Question Answers

Electric Current and its Effects is Chapter 14 taken from the JKBOSE textbook of Science for students of Class 7th. In the previous post, I provided you with Questions and Answers for Chapter 13 Motion and Time. This post is about Electric Current and its Effects Class 7 Question Answers. Before we proceed to Question Answers, you need to have basic information about the chapter. So here is a brief overview of the chapter:

Electric Current and its Effects Class 7 Question Answers

Overview of Chapter

• ELECTRIC CIRCUIT DIAGRAMS.
• HEATING EFFECT OF CURRENT.
• ELECTRIC FUSE.
• MAGNET I C EFFECT OF ELECTRIC CURRENT.
  1. Electromagnet.
  2. Uses of the electromagnet.
• ELECTRIC BELL.

ELECTRIC CIRCUIT DIAGRAMS: The standard method of drawing an electric circuit is termed a circuit diagram or electric circuit diagram. In the circuit diagram, various electrical components of the circuit are represented by standard symbols. These electrical components are termed elements of an electrical circuit.

HEATING EFFECT OF CURRENT: The production of heat in an electric device due to the flow of electric current is called the heating effect of electric current. The heating effect of current depends upon the resistance of the wire and the magnitude of current flowing through it.

ELECTRIC FUSE: It is a safety device which works on the heating effect of electric current. It is used in electric circuits to prevent electrical fires and damage to electric appliances due to the massive flow of electric current. The electric fuse works on the principle of the heating effect of current.

MAGNET I C EFFECT OF ELECTRIC CURRENT: When electric current passes through a wire, the current-carrying wire behaves like a magnet. It is called the magnetic effect of electric current. This effect of electric current is used on many devices of our daily use like electromagnets, electric bells, electric fans, toys etc.

1. Electromagnet: The magnet made by using electric current is termed an electromagnet. It works based on the magnetic effect of electric current.
2. Uses of an electromagnet: It is used in making many devices like electric fans, electric bells, electric motors etc.

ELECTRIC BELL: An electric bell works on the magnetic effect of electric current. It has an electromagnet in it.

That’s being said about the basics of this chapter. Now let us move on to the solutions section.

Chapter 14 Electric Current and its Effects Questions

Exercises.

A. Fill in the blanks:

1. A drawing of an electrical circuit with standard symbols is called a circuit diagram.
2. Hot plates, electric toasters, and electric irons get hot when switched on because of the heating effect of current.
3. A fuse is a safety device.
4. A wire twisted in the form of a circle is called a coil.
5. An electromagnet consists of a soft iron core with an insulated wire wound around it.

B. Choose the correct answer:

1. A circuit diagram is

(a) a picture of a circuit.

(b) a drawing of a circuit with standard pictures for the different electrical components.

(c) a diagram of an electrical circuit with standard symbols for the different electrical components.

(d) a difficult representation of an electrical circuit.

Ans. (c) a diagram of an electrical circuit with standard symbols for the different electrical components.

2. When an electric current pass through a wire, the wire gets hot. This is called

(a) Joule heating

(b) conduction

(c) electricity

(d) thermal heating

Ans. (a) Joule heating

3. An electric fuse is

(a) a safety device

(b) an appliance

(c) used to produce an electric current

(d) use to heat a room

Ans. (a) a safety device

4. When we bring a magnetic compass near a current-carrying wire,

(a) it deflects the magnetic needle of the compass

(b) it makes the magnetic needlepoint North

(c) it makes the magnetic needlepoint South

(d) it has no effect on the magnetic needle

Ans. (a) it deflects the magnetic needle of the compass

5. A coil refers to

(a) an electrical wire

(b) a fuse

(c) a current-carrying conductor

(d) a wire twisted in the form of a circle

Ans. (d) a wire twisted in the form of a circle

6. An electromagnet act like a magnet

(a) when a current is passed through the coil

(b) all the time

(c) because it has a magnetic core

(d) only if a current does not pass through the coil.

Ans. (a) when a current is passed through the coil

7. In an electric bell, we have

(a) an electromagnet

(b) a hammer

(c) an interrupter

(d) all of these

Ans. (d) all of these

8. In an electric bell, which of these gets attracted to the electromagnet?

(a) the hammer

(b) the gong

(c) the soft iron strip

(d) the screw

Ans. (c) the soft iron strip

9. Which of these does not use the heating effect of current?

(a) electric toaster

(b) electric fan

(c) electric Iron

(d) room heater

Ans. (b) electric fan

10. An electric fuse wire melts if the amount of current flowing through it is.

(a) more than a minimum amount

(b) less than a minimum amount

(c) more than a maximum amount

(d) less than a maximum amount

Ans. (c) more than a maximum amount

C. Answer the following questions.

1. What is an electrical circuit?

Ans. The continuous conducting path between two terminals of a cell or a battery along with electric current flowing through it is termed an electric circuit.

2. Draw an electrical circuit with an electrical cell, a bulb, and an ‘ON’ switch.

3. Why does an electric bulb get hot if it is kept ‘ON’ for a little while?

Ans. When an electric bulb is kept ‘ON’ for a while, it becomes hot. It is due to the heating effect of electric current.

4. Name three appliances that use the heating effect of electric current.

Ans. Following are the appliances that use the heating effect of electric current.

1) Electric toasters.

2) Electric ovens.

3) Electric hair dryers.

4) Hot plates.

5. What is an electric fuse?

Ans. It is a safety device which works on the heating effect of electric current. It is used in electric circuits to prevent electrical fires and damage to electric appliances due to the massive flow of electric current. The electric fuse works on the principle of the heating effect of current.

6. Draw an electric fuse and explain briefly how it works.

Ans.

An electric fuse works on the principle of the heating effect of electric current. The greater the current flowing in the circuit, the more heating is caused.

An electric fuse consists of a thin wire placed inside a glass or ceramic cartridge. The wire in the electric fuse is made up of material which melts on heating. It is designed in such a way that a certain maximum amount of current is allowed to flow through it. If the amount of current flowing in the circuit exceeds the maximum limit, the wire in the fuse melts away due to heating. As a result, the circuit breaks and the flow of current is stopped. It prevents electrical fires in case of short circuits or excessive flow of current in the circuit.

7. How can you show that an electric current has a magnetic effect?

Ans. We can show that electric current has a magnetic effect by performing the following activity:

Take the cardboard tray from inside a discarded matchbox. Wrap an electric wire a few times around the cardboard tray. Place a small compass needle inside it. Now connect the free ends of this wire to an electric cell through a switch as shown in the figure.

Now, while watching the compass needle carefully, move the switch to the ‘ON’ position. We will observe that the needle of the compass gets deflected. It shows that when electric current flows through an electric wire, it behaves like a magnet and shows a magnetic effect.

8. What is an electromagnet?

Ans. When an electric current is passed through a core (A piece of soft iron around which wire is wrapped), it behaves like a magnet. A magnet made by such an arrangement is known as an electromagnet.

9. Name two factors on which the strength of an electromagnet depends.

Ans. The strength of an electromagnet depends upon the following factors:

(i) Number of turns wound around the core.

(ii) Amount of current passing through it.

10. Explain the working of an electric bell using diagrams.

Ans. Working of an electric bell.

There are three steps in the working of an electric bell. These are as under:

Step 1. When you push the switch of the bell, the electric current flows to the electromagnet.

Step 2. The electromagnet attracts the soft iron strip. The hammer attached to the strip then hits the gong, causing a ring.

Step 3. When the soft iron strip gets attracted to the electromagnet, it no longer touches the screw (interrupter) and hence the circuit is broken, (much like a switch being turned off). This turns off the electromagnet and it can no longer attract the soft iron strip. The soft iron strip returns to its initial position, touching the screw (interrupter). This results in the circuit being complete and the current flowing again.

Steps 1 to 3 repeat in quick succession as long as the switch is on.

This is how we hear a continuous ring of the bell.