Question

Which of the following best characterizes ideal voltmeters and ammeters? (A) Ideal voltmeters and ammeters have infinite resistance. (B) Ideal voltmeters and ammeters have no resistance. (C) Ideal voltmeters have infinite resistance, and ideal ammeters have no resistance. (D) Ideal voltmeters have no resistance, and ideal ammeters have infinite resistance.

Short answer

Option C

Step-by-step solution

Understanding the Role of Voltmeters and Ammeters

Voltmeters measure the voltage across two points in a circuit, while ammeters measure the current flowing through a circuit. Ideal meters do not affect the circuit's functionality.

Ideal Voltmeter Characteristics

An ideal voltmeter should not draw any current from the circuit it is measuring. To achieve this, it must have infinite resistance.

Ideal Ammeter Characteristics

An ideal ammeter should not add any resistance to the circuit it is measuring. To achieve this, it must have no resistance.

Selecting the Correct Option

Based on the characteristics explained: ideal voltmeters need infinite resistance and ideal ammeters need no resistance. This matches option C.

Key concepts

Voltmeter Resistance

Voltmeters are devices used to measure the electric potential difference between two points in a circuit. To avoid changing the circuit's behavior, an ideal voltmeter must have infinite resistance. This is because:

• High resistance prevents the meter from drawing any current.
• No current draw means the voltage across the points being measured remains unaffected.

If a voltmeter had low resistance, it would divert current away, affecting the original circuit. In real-world scenarios, voltmeters have high, but not infinite, resistance, minimizing their influence on the circuit.

Ammeter Resistance

Ammeters measure the current flowing through a point in a circuit. Unlike voltmeters, an ideal ammeter must have no resistance at all. This ensures:

• No additional resistance is introduced to the circuit.
• The measurement does not alter the current flow.

If an ammeter had significant resistance, it would decrease the current passing through it, thus altering the circuit. Practical ammeters are designed with very low resistance to minimize their impact on the circuit.

Circuit Measurement

When measuring electrical properties in a circuit, using the correct ideal meters makes a big difference. Here’s a quick recap:

• Use a voltmeter with infinite resistance to measure voltage without affecting the circuit.
• Use an ammeter with no resistance to measure current without altering the circuit.

Understanding these principles is crucial for accurate measurement and maintaining circuit integrity. Always consider the meters' resistances and their potential effects on the circuit when performing real-world measurements.