If the potential difference across a coil is low, what will happen?

If the potential difference across a coil is low, what will happen?

• A. Draw too much current.
• B. Become too hot.
• C. Produce too much magnetic force.
• D. Not heat up.

Answer: (D)

When the voltage across a coil is low, the current through it is also small (Ohm’s law: I = V/R). Heat in the coil comes from power dissipated, P = I^2R (or P = V^2/R). If I is small, P is small, so the coil doesn’t heat up noticeably. The magnetic field the coil produces is proportional to the current, so with a small current you’d also get a weak magnetic effect. In short, low voltage yields little current, little power dissipation, and thus little heating.

When the voltage across a coil is low, the current through it is also small (Ohm’s law: I = V/R). Heat in the coil comes from power dissipated, P = I^2R (or P = V^2/R). If I is small, P is small, so the coil doesn’t heat up noticeably. The magnetic field the coil produces is proportional to the current, so with a small current you’d also get a weak magnetic effect. In short, low voltage yields little current, little power dissipation, and thus little heating.