Welcome to practical physicsPracticle physics - practical activities designed for use in the classroom with 11 to 19 year olds

Mounted transformers

You will need: 

  • Mains transformers, 230V to 12V 2A, 2. The ones used at present by a school may do but it is essential that they are double wound and preferably split-bobbin, e.g. RS Components 207-251 
  • 4 mm sockets, preferably yellow, 4 
  • Plastic boxes, with transparent lids, to take the transformer etc, 2 
  • Terminal block, standard screw terminal, 5A, e.g. RS Components 425-099 
  • Eureka (constantan) wire, 28 SWG, 3m 
  • Clear sleeving, 1.6 mm bore, e.g. RS Components 399-899, 3 m 
  • Wooden rod which will fit into a boss head on a stand, 40 cm
  • Connecting wire 

Technical notes

a Drill the boxes, each to take two 4 mm sockets. Make holes to mount the transformers and the terminal strips. 
b Solder connecting wires to both the high voltage and low voltage sides of the transformer. 

c Mount the transformers in the boxes; also part of the terminal block in each box. See diagram.Mounted transformers

d Connect the wires as shown. 
e Cut two lengths of wooden rod. Make slots to take the sleeved resistance wire. 
f Cut 1.5 metre lengths of the resistance wire and two lengths of the transparent sleeving about 1 cm shorter. These may be kept attached to a strip of wood with elastic bands, or coiled. 
g If it is considered essential to show the high voltage, holes may be drilled through the lid of the box to let multimeter probes contact the terminal block connections. 


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