Self Test


1.      An amplifier has an output resistance of 20 W.  It is to be match to a loudspeaker of resistance 8 W by a matching transformer.  What is the turns ratio?




2.      The primary coil in the transformer has 300 turns.  How many would the secondary have?





3.      The loudspeaker is rated at 25 watts.  What is the current?  What is the voltage?




4.      What is the voltage in the output of the amplifier?  What is the current?





5.      A transformer is connected to a 240 V AC supply to supply 12 V to a low voltage lighting system for a village on a model railway.  The total resistance of the system is 2.0 W.

a.       What is the ratio of turns N1:N2?

b.      What is the current in the secondary?

c.       What power is delivered to the load?

d.      What resistance, when connected to the 240 V supply will give the same power as the transformer?

e.       Show that the ratio of the source resistance to the load is the same as the square of the turns ratio.