Live Scope
Three synchronized traces: primary voltage (copper), magnetic flux proxy (grey), and secondary voltage (blue). Change frequency or turns above and the period and amplitude update immediately.
Energy Flow & Losses
Power in from the source splits between what the load receives and what is lost as heat in the windings (copper loss), heat in the core (hysteresis and eddy currents), and imperfect magnetic coupling (leakage). Values below use simplified educational assumptions.
Equation Explorer
Vs / Vp = Ns / NpThe turns ratio. Secondary voltage scales with the ratio of secondary turns (Ns) to primary turns (Np). Click a variable term below for a definition.
Select a variable to see its meaning.
Reveal Faraday's law (simplified)
V = N x (change in flux per second)Each turn of wire that the changing magnetic flux passes through contributes an equal induced voltage. More turns, more voltage. If the flux does not change (DC), no voltage is induced, which is why transformers need AC.
Reveal the power balance
Vp x Ip ~ Vs x IsPower is approximately conserved (ignoring losses). Step voltage up and current steps down by the same factor. Real transformers deliver a bit less than they draw because of copper, core and leakage losses.
Worked Examples
Can You Touch It?
The honest classroom answer: it depends entirely on the situation, and the safe default is no. Select the conditions to see a conservative risk explanation.
This simulator is educational only and is never a real-world safety test. Unknown or energized equipment must be handled only by qualified professionals following local procedures. Never touch electrical equipment to find out if it is safe.
Chapters
Faraday's law
A changing magnetic flux through a loop of wire induces a voltage proportional to the rate of change and the number of turns. This is the single principle a transformer is built on.
Alternating magnetic flux
AC in the primary drives a flux in the iron core that swings back and forth 50 or 60 times per second. That constant change is what continuously induces voltage in the secondary.
Turns ratio and step-up vs step-down
More secondary turns than primary turns: voltage steps up. Fewer: it steps down. Equal turns give an isolation transformer, useful for safety separation without changing voltage.
Losses
Copper loss is resistive heating in the windings (I squared R). Core loss comes from magnetizing the iron each cycle (hysteresis) and circulating eddy currents, reduced by laminating the core. Leakage flux is field that misses the other coil.
Frequency
Higher frequency means the flux changes faster, so a smaller core can transfer the same power. That is why phone chargers use high-frequency switching transformers and are so compact.
Why DC is different
Steady DC makes a steady flux. No change means no induced voltage, and the primary just heats up as a short circuit. Transformers only work with changing current.
Common misconceptions
A transformer does not create energy: stepping voltage up steps current down. Low voltage output does not mean the primary side is safe. Unplugged equipment can still hold stored energy in capacitors nearby.
Knowledge Check
Glossary
- Primary
- The input winding connected to the AC source.
- Secondary
- The output winding connected to the load.
- Core
- Laminated iron path that guides magnetic flux between coils.
- Flux
- The magnetic field passing through the coils, measured in webers.
- Induction
- Producing voltage from a changing magnetic field.
- Winding
- A coil of insulated wire wrapped around the core.
- Load
- The device drawing current from the secondary.
- Isolation
- Electrical separation between circuits with no direct wire connection.