Inside a phone charger, the outlet's 120 V must become about 5 V. But the charger's two coils are not even connected.
Earlier in this topic you saw the one condition for induction: an EMF is induced whenever the magnetic field through a conductor changes. That condition is the transformer's whole secret.
The supply drives an alternating current through the primary coil.
An alternating current reverses direction over and over. So the primary's current never stops changing.
The primary's current makes a magnetic field in the core.
The core carries that field around the loop, through the middle of the secondary coil.
The current keeps changing, so the field in the core keeps changing too.
The secondary coil sits in that changing field, and because the magnetic field through the coil is changing, an EMF is induced.
A transformer's primary coil carries an alternating current. What appears across its secondary coil?
That is how a phone charger passes power from the outlet side to the phone side with no wire linking its two sides.
Why is an EMF induced in the secondary coil while AC flows in the primary?
AC flows in the primary coil of a doorbell transformer. State why an EMF appears across its secondary coil.
The alternating current keeps changing.
So the magnetic field in the core keeps changing.
The field through the secondary coil is changing, so an EMF is induced in the secondary coil.
An EMF appears across the secondary because the field through it keeps changing.
The two coils of that transformer have no electrical connection. What carries the power across?
The primary's changing current makes a changing field in the core.
The core's changing field induces an EMF in the secondary.
The changing magnetic field in the core carries the power across.
A transformer's coils have no electrical connection. What carries the power from coil to coil?
An electric toothbrush charges on a stand with no metal contact: a coil in the stand carries AC, and a coil in the brush sits just above it. Why does the brush's coil gain an EMF?
AC flows in a transformer's primary, and an EMF appears across the secondary. Which step links the two?
A transformer hums on a utility pole; its primary carries AC from the street line. Which sentence says how power reaches its secondary coil?