Question

an ideal voltmeter, when connected in parallel, should not affect the overall circuit. what is the ideal resistance of a voltmeter?

same as the internal resistance of the power source
infinite resistance
zero resistance
same as the resistance of the part it is parallel to

Explanation:

Analyze voltmeter connection

An ideal voltmeter measures potential difference.
It connects in parallel.

Determine current draw

To not affect the circuit,
it must draw zero current.
Current through it must be zero.

Apply Ohm's law

Using Ohm's law, \(I = \frac{V}{R}\).
For \(I\) to approach zero,
\(R\) must approach infinity.

Evaluate the options

Infinite resistance prevents current diversion.
This keeps the circuit unchanged.
Thus, ideal resistance is infinite.

Answer:

• Same as the internal resistance of the power source
• Infinite resistance (Correct answer)
• Zero resistance
• Same as the resistance of the part it is parallel to