# Electrical Current

Lesson Planning of Electrical Current

Subject General Science

Students` Learning Outcomes

• After studying this lesson, students will be able to:
• Describe the flow of electric current in an electrical circuit.
• Describe a fuse and its importance in an electric circuit.

Science Processing Skills

Observing, Classifying, Communicating, Inferring, Predicting and Experimenting

Information for Teachers

• Electric current is a physical phenomenon caused by the displacement of a charge (ion or electron).The intensity of the current is the amount of charge that passes through a conductor per unit of time. The intensity of the current is measured in Amps (A)

Simple Circuit: The path, along which electricity flows, is called circuit.

• Electricity can flow only if the circuit is closed or complete.
• If the circuit is open or broken, electricity can`t flow through it.
• A cell is a source of electricity. It has two terminals, one terminal is called positive and other negative.

• The material which don`t let the bulb glow, it can`t conduct electricity. The iron or copper wires and other metallic objects are conductors while the materials like wood, rubber, and plastic are insulators.

• A battery cell is shown in the figure. Battery cells are used in TV remote controls, in torches, in toys and in many other appliances. One end of the cell is positive and the other end is negative. Actually there is an excess of electrons at the negative end and a deficiency of electrons at the positive end. When the two ends of the cell are connected through a wire or a conductor, electrons start flowing from where they are in excess towards the point of deficiency. This flow of electrons is called an electric current, so we can say that an electric current is the flow of charges.

Material / Resources

Writing board, chalk / marker, duster, a bulb with a holder, a switch, two battery cells and connecting wire, steel wool or thin metallic wire, glass plate

Introduction

• The lesson may be started with a discussion such as;

1.      Have the students seen a battery cell?

2.      Where are they used?

3.      List the devices or appliances in which battery cells are used.

4.      Are there other sources of electric current?

5.      Name the other sources and their uses.

Development

Electric Currents

Activity 1

• How can we know whether the current is flowing or not? Let us perform an activity.

Material Required

A bulb with a holder, a switch, two cells and connecting wires

Methods

• Divide the class into suitable groups and tell them to follow the given instructions:

1.       Connect a bulb, a switch and a cell with the help of connecting wires as shown in the figure.

2.       What do you think would happen if we turn the switch on?

3.       Turn the switch on and observe the bulb, does it glow?

4.       What do you think would happen if we switch off current?

5.       Turn the switch off and observe if the bulb still glows.

6.       Why does the bulb glow when the switch is on?

Fuse and its uses

Background Information

• A fuse is inserted into an electric circuit as a protecting device. Each fuse is rated for a maximum value of current. Only that amount of current and can pass through a fuse safely that is mentioned on it. If more current passes through it, the fuse blows out. Our electric appliances are connected in electric circuits. Each appliance runs with a certain amount of current. If large current passes through it, the appliance may burn out in case the fuse is not used.

• A suitable fuse is inserted in the circuit of an appliance. If, excess current flows through the circuit, the fuse blows out and the appliance is protected.

The safe use of electricity

Background Information

• Start the lesson by mentioning the use of electricity to run our television, our fans, our refrigerator and many other appliances. Many times we have heard fatal accidents, fires and people getting electricity shocks while using electricity without safety precautions.  Let us investigate the safe use of electricity, how to protect the appliances and how to avoid fire hazards using a fuse in an electric circuit.

Material / Resources

Two cells, a bulb, steel wool  or thin metallic wore, glass plate and connecting wire

Method

• Divide the class into suitable groups and tell them to follow given instructions:

1.       Combine two or three cells to make a battery.

1.       Join two connecting wires to both ends of the battery.

2.       Place a thin fiber of steel wool on a glass plate. If it isn`t available, a piece of very thin metallic wire (of low melting point) can be used.

3.       Touch copper wires on both sides of the thin wire. Does it burn out after becoming red hot?

• The thin wire burns out because a large current starts flowing through it. The thin wire becomes so hot that it melts immediately. Such a piece of wire is called fuse.

Sum up / Conclusion

Conclude the lesson with briefly revise the topic.

Assessment

1.       Match Column (A) with column (B)

 A B i)                    Direction ii)                   Path iii)                 Fuse i)                    Electric current ii)                   Thin metal wire iii)                 Electric Circuit

2.       Encircle the correct answer from the following:

A. An electric current is

i.                     The flow of heat

ii.                   The flow of light

iii.                  The flow of charges

iv.                 The flow of atoms

B. To save an appliance from burning out we use:

i. A switch

ii. A fuse

iii. A bulb

iv.               A battery cell

3.       What s an electric current? Describe a simple activity to show that a current can flow only through a closed circuit.

4.       Why a metallic wire of low melting point is is used for the fuse?

5.       What are the advantages of using a fuse in an electric circuit?

6.       Suppose you turn on an electric iron in your home and all the lights in your room go out. Give a reason why the lights went out?