What is the transformer turns ratio?

V_p/V_s = N_p/N_s, where N_p and N_s are the number of turns in the primary and secondary coils. Step-up: N_s > N_p. Step-down: N_s < N_p.

Why are transformers AC only?

Transformers rely on a changing magnetic flux to induce an EMF in the secondary. A steady DC current produces a constant flux and no induced EMF.

What does ideal transformer mean?

100% efficient: V_p I_p = V_s I_s exactly. Real transformers lose a small amount of energy to resistance (I²R heating) and to eddy currents and hysteresis in the iron core.

Why use a step-up transformer for power transmission?

Higher voltage means lower current for the same power (P = VI). Lower current reduces I²R losses in transmission lines, which is why long-distance power lines run at hundreds of kilovolts.

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Transformer calculator

Q: Why are transformers AC only?

Transformers rely on a changing magnetic flux to induce an EMF in the secondary. A steady DC current produces a constant flux and no induced EMF.

Q: What does ideal transformer mean?

100% efficient: V_p I_p = V_s I_s exactly. Real transformers lose a small amount of energy to resistance (I²R heating) and to eddy currents and hysteresis in the iron core.

Q: Why use a step-up transformer for power transmission?

Higher voltage means lower current for the same power (P = VI). Lower current reduces I²R losses in transmission lines, which is why long-distance power lines run at hundreds of kilovolts.

Ideal transformer relations V_p/V_s = N_p/N_s and V_p I_p = V_s I_s. Solve for any of V_p, V_s, I_p, I_s given the others.

Inputs

Solve forPrimary turns N_pSecondary turns N_sPrimary voltage V_p (V)Secondary voltage V_s (V)Primary current I_p (A)Secondary current I_s (A)

Result

Secondary voltage V_s

12.00V

Ideal transformer: V_p/V_s = N_p/N_s, and V_p I_p = V_s I_s. A step-up transformer has N_s > N_p.

How this calculator works

The calculator applies the turns ratio for voltage, and conservation of power (V_p I_p = V_s I_s) for current, assuming 100% efficiency. Real transformers achieve 95-99% in practice.

Common questions

What is the transformer turns ratio?: V_p/V_s = N_p/N_s, where N_p and N_s are the number of turns in the primary and secondary coils. Step-up: N_s > N_p. Step-down: N_s < N_p.
Why are transformers AC only?: Transformers rely on a changing magnetic flux to induce an EMF in the secondary. A steady DC current produces a constant flux and no induced EMF.
What does ideal transformer mean?: 100% efficient: V_p I_p = V_s I_s exactly. Real transformers lose a small amount of energy to resistance (I²R heating) and to eddy currents and hysteresis in the iron core.
Why use a step-up transformer for power transmission?: Higher voltage means lower current for the same power (P = VI). Lower current reduces I²R losses in transmission lines, which is why long-distance power lines run at hundreds of kilovolts.