CORRECT!

First of all, the only flight instruments required for VFR day flight are the airspeed indicator, altimeter and compass. This implies that the best way to control an aircraft under VFR conditions is to look outside. That said, the gyroscopic instruments (attitude indicator (AI), directional gyro (DG) and turn coordinator (TC)) provide useful information for controlling the aircraft, especially in the event of inadvertent flight into instrument meteorological conditions. The AI and DG are vacuum-driven gyros, deriving the vacuum power from the operable engine. The TC, on the other hand, is usually driven by an electric-powered vacuum (note the placard 'D.C. ELEC.' at the top of the instrument).

Thus, if either the electrical system or the engine-driven vacuum system were to fail, the instrument powered by the other still-operable system would provide the bare minimum of information to the pilot for aircraft control.

One way to check the health of the electric-powered gyro (usually the TC) is to switch the electrical system on and listen to the sound of the electric gyro 'spooling up'. If there are grating sounds or other indications of labored operation, the gyro is probably reaching the end of its useful life.