When DC voltage is applied to a coil (or winding), how does the strength of the magnetic field change?

When DC voltage is applied to a coil (or winding), how does the strength of the magnetic field change?

• A. It becomes variable
• B. It is constant
• C. It decreases
• D. It increases

Answer: (B)

When DC voltage is applied to a coil or winding, the strength of the magnetic field produced is constant after an initial transient period. Initially, when the DC voltage is first applied, the current flowing through the coil increases until it reaches a steady state, which creates a magnetic field. Once this steady state is established, the current and, consequently, the magnetic field strength remain stable as long as the applied DC voltage does not change. This characteristic of DC is what differentiates it from AC voltage, where the current and magnetic field continuously vary with time due to the alternating nature of the voltage. Thus, in the context of a coil energized with DC, once the current stabilizes, the magnetic field strength does not fluctuate, making it constant.

When DC voltage is applied to a coil or winding, the strength of the magnetic field produced is constant after an initial transient period. Initially, when the DC voltage is first applied, the current flowing through the coil increases until it reaches a steady state, which creates a magnetic field. Once this steady state is established, the current and, consequently, the magnetic field strength remain stable as long as the applied DC voltage does not change. This characteristic of DC is what differentiates it from AC voltage, where the current and magnetic field continuously vary with time due to the alternating nature of the voltage. Thus, in the context of a coil energized with DC, once the current stabilizes, the magnetic field strength does not fluctuate, making it constant.