Electrical Circuits

Resources Needed:

1 lemon or lime 1 iron screw 5 cm long 1 brass screw 5 cm long

1.5 volt light bulb 3 insulated wires with striped ends approx. 15 cm D cell battery

1 D cell battery holder 1 light bulb holder comb

penny rock metal spoon fabric

BATTERIES

           Batteries are assembled from cells, connected in series, to increase the voltage available.
          In a cell, chemical energy is converted into electrical energy.
          Cells may be either PRIMARY or SECONDARY types.
          A primary cell is discarded when its chemical energy is exhausted.
          A secondary cell can be recharged.
          The most common primary cell is the zinc/carbon (Leclanche) as used in torches, portable radios etc. 

1.  Building your own battery.  

Demonstrate your battery to the class. Click here for directions.

2.  Using two or three wires, one battery, and one light bulb, build a simple circuit, a parallel circuit, and a series circuit.

     Click here for diagrams.
    For more basic electronics diagrams and explanations 

 VOCABULARY

• circuit a closed loop of conductors through which charges can flow

• conductor a substance through which electrical charges can easily flow

• current a flow of electrical charges

• generator a device for producing electrical current by moving a coil of wire in a magnetic field

• insulator a material through which electric charges cannot move

• ion an atom that has gained or lost one or more electrons and is thus a charged particle

• switch a device that closes or opens a circuit, thereby allowing or preventing current flow

• voltage the pressure behind the flow of electrons in a circuit

4.  Visit Frankenstein's Lightning Lab. on electrical safety. 

Place the cursor on a part ot the house to learn a safety rule.

Make a poster which illustrates one of the safety rules.  Click here to go to Frankenstein's Lab

CONDUCTORS

           These are materials in which it is easy to get electrons to move and provide a flow of electric current.
          Conductors are mostly metals such as gold, silver, copper, iron and lead.
          Carbon is a conductor as well as some gases (as in fluorescent tubes) and water containing some chemicals.
          These are not perfect conductors and offer some resistance to the flow of current. 

           The resistance of a conductor (such as a metal rod) is determined by three things: 

           (1) its length. The longer its length the higher its resistance.
          (2) its cross-sectional area. The bigger this is the lower is its resistance.
          (3) the material of which it is made. 

           All materials have RESISTIVITY.
        The higher the value of resistivity the higher the resistance.
        It is measured in OHM METERS. 

                                            length x resistivity
            Resistance  =     -------------------------------
                                            cross-sectional area

6.   The measure of energy per unit charge is measured is called voltage (V) and the unit of measurement is called volts.

     Resistance inhibits the amount of current running along the circuit. 

     Use the voltage simulator to light the light bulb. 

     Record  your results. Voltage Circuit Simulator

Thanks to
Graham Knott,
27 Edinburgh Road,
Cambridge, CB4 1QR