On the parallel conductors shown below,
a. Using a plus and minus sign, label the polarity of the induced voltage in conductor B when the switch is
b. Using an arrow, indicate the direction of current flow through the meter when the switch is closed.
Which two symbols indicate mutual inductance.
So far, the effect of mutual inductance has been discussed only as it apples to d-c circuits. This effect
occurs only when the circuit is turned on or off, because that is the only time the magnetic field is changing.
However, mutual inductance has a much greater and more useful effect in an a-c circuit, because the
current in an a-c circuit is constantly changing. By placing a coil of wire near another and by applying an a-
c voltage to the first coil, an a-c voltage is induced into the second coil. This device is known as a
TRANSFORMER. Coils are used in transformers because a stronger magnetic field is produced by a coil
than by a straight piece of wire. Transformers are used to transfer a-c electrical energy from one circuit to
another by mutual inductance.