alleryStart learning →Which sensor, operating at liquid helium temperature, can measure fields thousands of times smaller than that of the Earth?
AA Hall probe
BA SQUID detector
CA compass needle
DA galvanometer
Answer & Solution
Correct answer: B. A SQUID detector
1. Magnetic fields from the heart and brain are far weaker than that of the Earth.
2. Detecting them needs a sensor called a SQUID, short for superconducting quantum interference device.
3. It operates at liquid helium temperature.
4. It can measure magnetic fields thousands of times smaller than that of the Earth.
5. A Hall probe is accurate but nowhere near sensitive enough for these signals.
_Source: OpenStax College Physics (CC BY 4.0), Ch 22 "Magnetism", section 22.11 More Applications of Magnetism_
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