P7: TRANSFORMERS Flashcards
What is a transformer?
a device that can change the pd/voltage of an alternating current
What does a step-up transformer do?
-increases voltage, decreases current
(-to reduce energy being lost as heat)
What does a step-down transformer do?
-decreases voltage, increases current
-for safety reasons
How do transformers work?
-Current flows through the primary coil
it generates a changing magnetic field
-This magnetic field is transmitted along
the iron core and it passes through the
secondary coil
-When the changing magnetic field passes through the secondary coil it induces a potential difference
How do step-up transformers increase pd?
more turns on secondary coil (compared to primary coil)
How do step-down transformers decrease pd?
more turns on primary coil (compared to secondary coil)
What is the equation linking pd in primary coil, pd in secondary coil, no. of coils in primary coil and no. of coils in secondary coil?
pd in primary coil (V) / pd in secondary coil(V) = no. of coils in primary coil / no. of coils in secondary coil (Vp/Vs = Np/Ns)
Why does Vp/Vs = Np/Ns?
because the ratio between the primary and the secondary pds is the same as the ratio between the no. of turns on the primary and secondary coils