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PRIOR KNOWLEDGE


Specific Objectives

By the end of this topic you should be able to:

  • Set up simple electric circuits
  • Identify circuit symbols
  • Define electric current

TOPIC :CELL AND SIMPLE CIRCUITS

SUB/TOPIC: SIMPLE ELECTRIC CIRCUITS


Activity 2

Drag a conducting wire so that it connects the positively charged body and the negatively charged body


An electric current is produced when charges move in a definite direction.
A complete path along which the charges flow is called Electric circuit
.     


To maintain a continuous flow of charge a cell is used.  It supplies electrical energy which drives the electrons round the circuit.



 

Simple Electric Circuit

Drag and drop the dry cell, the switch and the bulb into the gap A, B and C respectively.
What happens to the bulb?  Type the answer in the box


Observation

 

Once the circuit is complete with items in place the bulb lights

Drag to remove the cell from the circuits.  Observe what happens to the bulb.

Drag the cell back to its place, so that the bulb lights.

Drag and remove the switch so that the wires are not connected.  What happens to the bulb?

Conclusion

When the circuit is complete the bulb lights.

When the circuit is not complete the bulb does not light


Activity 4

Click the switch in the circuit below so that the circuit is complete.  Observe what happens tothe bulb?



Electrons flow from the negative terminal of the cell to the positive terminal through the connecting wire.
By convection the current is considered to flow to flow from positive terminal to the negative terminal through the connecting wires.


 

Activity 4

Click the switch in the circuit below so that the circuit is complete.  Observe what happens tothe bulb?



Electrons flow from the negative terminal of the cell to the positive terminal through the connecting wire.
By convection the current is considered to flow to flow from positive terminal to the negative terminal through the connecting wires.


 

Activity 5:Circuit symbols

Circuit symbols are used instead of real pictures of the components

Components and their symbols

Activity 6: Arrangement of cells in series

Drag and drop a cell in gap x and the wire in gap y so that the circuit is complete
Observe the brightness of the bulb.
Drag the wire out and replace it with another cell so that the positive of one cell is connected to the negative of the other cell. This arrangement is called series arrangement.



 

Cells in parallel

Drag and drop a cell in gap A

Observe the brightness of the bulb.
Drag and drop a cell in gap B followed by gap C each time observing the brightness of the bulb.  Positive ends of the cell should face the same direction.  They are said to be in parallel.


Activity 7: Arrangement of bulbs in series


Click on the bulb, then drag and drop it in gap A.
Click on the wires then drag and drop them in gaps B and C so that the circuit is complete.  Observe the brightness of the bulb.
Drag wire on gap B away and Drag and drop a bulb in gap B.
Observe the brightness of the two bulbs.
Drug away the wire in gap C and replace it with a bulb so that you have three bulbs in series.
Observe the brightness of the bulbs.


Bulbs in parallel

Drag and drop a bulb in gap x.
Observe the brightness of the bulb.
Drag and drop a bulb in gap y and z respectively each time observing the brightness of the bulb.

Fill the gaps in the table by dragging the words brighter or same brightness in the spaces

The brightness of the bulbs remain the same throughout

Drag out the bulb in gap y.
What happens to the others?
Their brightness increases

The brightness of a bulb is a measure of how much electric current is passing through it.
If bulbs are in parallel a fault in one bulb does not affect the others.


Electric Current

Electric current is defined as the rate of flow of charge.
The symbol for current is I.

Current is measured in amperes. Symbol for amperes is A.
Current = Charge flowing/time taken
I =   Q/t  or  Q= It
The S.I. unit of charge is Coulomb.


You are provided with the following

Bulb- A, Bulb - C and Cell

Activity 5:Circuit symbols

Circuit symbols are used instead of real pictures of the components

Some Components and their symbols

Activity 6: Arrangement of cells in series

Drag and drop a cell in gap x and the wire in gap y so that the circuit is complete
Observe the brightness of the bulb.
Drag the wire out and replace it with another cell so that the positive of one cell is connected to the negative of the other cell. This arrangement is called series arrangement.



 

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