Which statement is true regarding non-contact voltage detectors?

Non-contact voltage detectors are designed to sense the presence of voltage without needing to make direct contact with the electrical conductor. They operate by detecting the electric field generated by the voltage present in a wire or cable.

When considering the correct statement, knowing that non-contact voltage detectors typically cannot detect voltage in shielded cables is important. Shielded cables have an outer conductive layer (the shield) designed to block external electromagnetic fields from affecting the signal carried by the internal conductor. This shielding can prevent the detector from sensing the electric field emanating from the wire inside, resulting in a failure to detect voltage in these types of cables.

While non-contact voltage detectors are effective for testing AC voltage due to the nature of how they sense voltage, this specificity does not relate to their ability to detect voltage in shielded cables. Their advantage lies in their non-invasive method, which is particularly beneficial for safety, as it reduces the risk of electric shock or accidental short circuits.

The statement that non-contact voltage detectors can only test AC voltage also adds a layer of misunderstanding, as some advanced models may yield accurate readings for both AC and DC under the right conditions.