Which of the following instruments can detect the presence of a current in a circuit?

Galvanometer

The correct answer is option 1. Galvanometer.

The instrument that can detect the presence of a current in a circuit is Galvanometer.

A galvanometer is a device used to detect and measure electric current. It works based on the principle of electromagnetic induction or the interaction between a magnetic field and an electric current. When current flows through a galvanometer, it produces a deflection of a needle or pointer on a scale, indicating the presence and magnitude of the current. Galvanometers are commonly used in various electrical and electronic circuits for measuring current.

The other options mentioned, such as sphygmomanometer, barometer, and magnetometer, are instruments used for different purposes:

Sphygmomanometer: It is used to measure blood pressure.

Barometer: It is used to measure atmospheric pressure.

Magnetometer: It is used to measure the strength and direction of magnetic fields.