Question

Why can't a transformer be used to step up or step down the voltage in a DC circuit?

Short answer

Answer: A transformer cannot be used to step up or step down the voltage in a DC circuit because its working principle relies on the constantly changing magnetic field induced by the alternating current in the primary coil. In a DC circuit, the current and magnetic field are constant, and no induced EMF is generated in the secondary coil, rendering the transformer ineffective for voltage regulation in DC circuits.

Step-by-step solution

Understand the working principle of a transformer

A transformer works on the principle of electromagnetic induction, where a change in the current in one coil (primary coil) produces a change in the magnetic field around it, thus inducing an electromotive force (EMF) in the second coil (secondary coil). This concept relies on the fact that the current and the magnetic field are continuously changing with time in AC circuits, allowing the transformer to step up or step down the voltage.

Understand the difference between AC and DC circuits

In an alternating current (AC) circuit, the current repeatedly changes its direction and magnitude, resulting in a constantly changing magnetic field. Conversely, in a direct current (DC) circuit, the current flows in one direction and has a constant magnitude. The magnetic field in a DC circuit also remains constant and does not change with time.

Analyze the working of a transformer in a DC circuit

As previously stated, the working of a transformer relies on the constantly changing magnetic field produced by the change in current and its direction in an AC circuit. In a DC circuit, the current and the magnetic field are constant, which means that there is no induced electromotive force (EMF) in the secondary coil of the transformer since there is no change in the magnetic field.

Conclusion

A transformer cannot be used to step up or step down the voltage in a DC circuit because its working principle relies on the constantly changing magnetic field induced by the alternating current in the primary coil. In a DC circuit, the current and magnetic field are constant, and no induced EMF is generated in the secondary coil, rendering the transformer ineffective for voltage regulation in DC circuits.