Final answer:
Reversing the battery in a circuit will cause the voltmeter to read a negative voltage, as the current direction changes but the magnitude of the voltage remains the same. The multimeter mode must match the measurement type to avoid affecting the circuit or damaging the meter.
Step-by-step explanation:
If the direction of the battery is switched in an electrical circuit, the polarity of the voltage measured by the voltmeter will change. In this scenario, when the leads of the battery are reversed, the current will flow in the opposite, or counterclockwise, direction. This will result in the voltmeter giving a negative reading as opposed to a positive one when the battery was oriented initially. The direction of the current flow is crucial here, as it determines the sign that the voltmeter will display. Moreover, it is important to note that the magnitude of the voltage remains the same; only its polarity changes.
Instruments like a multimeter need to be set correctly for the measurement being taken; otherwise, they can affect the circuit. For example, if a multimeter is set to measure voltage (voltmeter mode) but is used to measure current, it may introduce high resistance into the circuit, as voltmeters are designed to have high resistance to minimize their impact on the circuit's voltage. Conversely, if it's inadvertently left in ammeter mode while attempting to measure voltage, it could present a very low resistance path potentially causing a short circuit and damaging the meter or the circuit components.