Question

Does a step up transformer contradict the principle of conservation of energy? Justify your answer.

Hint:

Think of a transformer like a see-saw: if one side (Voltage) goes up, the other side (Current) must go down to keep the system in balance. You never get "free" power!

Answer 1

Step 1: Core Answer.
No, a step-up transformer does not contradict the principle of conservation of energy. While it increases (steps up) the voltage in the secondary coil, it does so at the expense of the current.

Step 2: Justification through Power Equality.
According to the law of conservation of energy, for an ideal transformer (with no energy losses), the input power must equal the output power: $$P_{primary} = P_{secondary}$$ Since Power ($P$) is the product of Voltage ($V$) and Current ($I$): $$V_p I_p = V_s I_s$$
Step 3: Relationship between Voltage and Current.
In a step-up transformer, the secondary voltage ($V_s$) is greater than the primary voltage ($V_p$). To maintain the equality $V_p I_p = V_s I_s$, the secondary current ($I_s$) must be proportionally smaller than the primary current ($I_p$): $$\frac{V_s}{V_p} = \frac{I_p}{I_s}$$ Thus, as voltage is "stepped up," current is "stepped down," ensuring that the total energy (power over time) remains constant. In real-world transformers, the output power is actually slightly less than the input power due to heat and flux losses, further proving that energy is never "created."