Question

Which statement about the ends of a solenoid versus a toroid is correct?

Options

• A solenoid has ends where \(B = \frac{\mu_0 nI}{2}\), while a toroid has no ends because it is a closed loop

• Neither a solenoid nor a toroid has ends, as both are closed structures

• Both a solenoid and a toroid have ends where the field drops to half

• A toroid has two ends where the field is \(\frac{\mu_0 nI}{2}\), while a solenoid has no ends

Answer 1

A solenoid is a long straight cylinder and therefore has ends, where the field is \(B = \frac{\mu_0 nI}{2}\). A toroid is a solenoid bent into a closed ring (doughnut shape) and has no ends (closed loop), so the end-effect does not arise for a toroid.