Question 3 of

What must you do before measuring resistance with a Digital Multimeter (DMM)?

AUse an external battery instead of the DMM's internal battery.
BClose all switches and connectors in the circuit being measured.
CChange the DMM's resistance measurement to display two decimal places.
DEnsure the circuit has power and is connected to parallel circuits.

Before measuring resistance with a Digital Multimeter, you must ensure the circuit being tested is de-energized by closing all switches and connectors. This is essential to obtain accurate readings and prevent damage to the DMM. The correct choice is option B.

Explanation:

Measuring Resistance with a Digital Multimeter (DMM)

Before measuring resistance with a Digital Multimeter (DMM), it is crucial to ensure that the circuit being tested is not powered. This is because a live circuit can give inaccurate readings and potentially damage the DMM. Therefore, the correct answer to the question is:

Correct Action

B) Close all switches and connectors in the circuit being measured.

This step ensures that there is no current flowing through the circuit when you take the resistance measurement, thus allowing for an accurate reading. Other options, such as using an external battery or ensuring power to the circuit, would lead to incorrect readings.

Why It Matters

When measuring resistance, the DMM uses its internal battery to pass a small current through the component. If the circuit is energized, the DMM cannot accurately measure the resistance since other variables (like the voltage from the power source) interfere with the measurement.

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