I understand how to make and draw a circuit, and explain how it works.
Discuss your drawings of torches from yesterday- what are pros & cons of the drawings
New Information 1:
ROLE PLAYING A CIRCUIT
So…how is an electrical circuit created?
A circuit needs 3 parts-
- a cell to give energy,
- a conductor to conduct the energy,
- a resistor/load to use up the energy- What are some types of resistors?light bulb, bell, buzzer or motor
When you connect the negative end of the cell with the positive end using a conductor (wire) and have a resistor/load in the middle, you have a complete circuit. Electricity will only travel in a current if the circuit is complete and has no break.
A ‘cell’ contains chemicals. When the chemicals in the cell react, they release energy. This energy gives the electrons in the atoms at the negative end (electrons are negatively charged) an energetic ‘push’.
This energy is carried around the circuit by the electrons to the resistor where the electrical energy is changed into another form of energy, such as light, sound, heat or movement.
The current of electrons then continues having lost its extra energy, through the circuit to the positive end of the cell.
The circuit can be repeated over and over as long as the chemical reaction continues.
Electrons flow through a circuit and are not consumed. It is the electrical energy they carry that is changed into other forms of energy, such as heat and light; nothing is used up or consumed, just changed.
When a torch switch is turned on, it completes the electric circuit, making a complete path for the electrons to flow around.
If you don’t have a cell you have no energy to start things going …..
If you don’t have a conductor, you don’t have anything for the energy to travel along to complete the circuit …..
If you don’t have a resistor, the energy created in the cell doesn’t get used up-if this happens then the energy will come out as heat in the conductor and burn up!-this is called a ‘short circuit’– and is the major cause of electrical accidents …..
You can have many of these parts-many cells (becoming a ‘battery’)/ many conductors- wires in many parts of the circuits/ many resistors – such as a series of lights or lights and buzzers etc
Vocab: electrons, circuit, positive and negative terminals, battery/cell, switch, movement, light and sound resistors, conductors and insulators, chemicals, chemical reaction, current short-circuit
more information available here if students want to clarify or research further:
Discuss and make connections to the role play- what parts were what?
Draw a circuit from the demonstration and explanation
New Information 2:
Scientists use a series of symbols to represent the parts of a circuit- why do you think they do this?
Show symbols (students paste in books):
Discuss open/closed switch & difference between cell & battery.
Discuss what voltmeter & ammeter might measure. (not needed at this level)
Look at these 2 diagrams- T&T- what are the similarities & differences
Which do you prefer? why?
Which do you think scientists prefer? why?
It is important to draw circuits with clean straight lines, as shown in diagram B. Scientists avoid realistic sketches like diagram a-why?
Student review their cutaway diagram of how a torch could work from the last lesson and update or redraw this diagram to include what they now know, such as names/symbols of parts and the need for a complete circuit for the torch to light.
Share & discuss
MORE LIKE ONE OF THESE-
Introduce snap circuit sets. Show how the symbols for the items are ON the items. Show how they snap together and the many possible circuits that can be created.
In groups of 3 or 4, students should make a circuit using circuit items available.
Once made, student & tested (troubleshoot where necessary), students should make a technical diagram of their circuit using the symbols they have learned. They should give it a title saying what it does. (Students should have labeled the basics – cell/battery, wires, item that uses power/switch
IT IS IMPERATIVE THAT STUDENTS ARE DILIGENT NOT TO CREATE SHORT CIRCUITS- NO BATTERIES SHOULD BE PUT IN PLACE IN THE CIRCUIT UNTIL IT HAS BEEN DRAWN AND SEEN BY A TEACHER TO ENSURE AGAINST SHORT CIRCUIT.
Circuits should then be tested and troubleshot if necessary
If there’s time, students can make another circuit
3 important facts I remember
2 connections I made during the lesson
1 question I still have