NCERT solutions for Science [English] Class 7 chapter 10 - Electric Current and Its Effects [Latest edition]

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.

Draw the circuit diagram to represent the circuit shown in the figure.

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.

The bulb in the circuit shown in Figure does not glow. Can you identify the problem? Make necessary changes in the circuit to make the bulb glow.

Name any two effects of electric current.

When the current is switched on through a wire, a compass needle kept nearby gets deflected from its north-south position. Explain.

Will the compass needle show deflection when the switch in the circuit shown by figure is closed?

Longer line in the symbol for cell represents its ______ terminal.

The combination of two or more cells is called a ______.

When current is switched ‘on’ in a room heater, it ______.

The safety device based on the heating effect of electric current is called a ______.

To make a battery of two cells, the negative terminal of one cell is connected to the negative terminal of the other cell.

When the electric current through the fuse exceeds a certain limit, the fuse wire melts and breaks. 

An electromagnet does not attract a piece of iron.

An electric bell has an electromagnet. 

Do you think an electromagnet can be used for separating plastic bags from a garbage heap? Explain.

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.

Zubeda made an electric circuit using a cell holder shown in Figure, 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.

In the circuit shown in figure would any of the bulbs glow when the switch is in the ‘OFF’ position? 

In the circuit shown in figure, what will be the order in which the bulbs A, B and C will glow when the switch is moved to the ‘ON’ position?

Set up the circuit shown in Figure again. Move the key to ‘ON’ position and watch carefully in which direction the compass needle gets deflected. Switch ‘OFF’ the current. Now keeping rest of the circuit intact, reverse the connections at the terminal of the cell. Again switch ‘on’ the current. Note the direction in which the needle gets deflected. Think of an explanation.

Make 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.

Using an electromagnet, you can make a working model of a railway signal as shown in figure.

Visit an electric shop. Request an electrician to show you the various types of fuses and MCB and to explain how they work.