Unlike the idealized voltmeter, a real voltmeter has a resistance that is not infinitely large.

Question

A voltmeter with resistance RV is connected across the terminals of a battery of emf E and internal resistance r. Find the potential difference V_meter measured by the voltmeter.

What is V_meter?

[su_box title="♦ Relevant knowledge" box_color="#2d6ff7" radius="1"]From a theoretical point viewpoint, an ideal battery is able to supply an unvarying voltage to the circuit, which isn't affected by the current flow within the circuit. This phenomenon is explained by having an internal resistor which is, in ideal terms, in the range of zero. This means that all voltage is directly pumped towards the device. The battery in the real world differs because it has a lower internal resistance, it has an impact in the direction of the current it can influence the possible decrease in resistance to the load.

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lyytutoria · Accepted Answer

lyytutoria · Answer

Sophia Roberts · Answer

Concepts and Reason

Kirchhoff's loop rule, and ohms' law are the concepts that were used to solve this problem.

The Kirchhoff's loop rule can initially be used to calculate the current through the circuit.

The ohm’s law for circuits can be used to calculate the potential difference between the voltmeter and the circuit.

Fundamentals

Kirchhoff's loop rule says that the sum voltage across all circuit elements will equal zero.

The circuit diagram of the voltmeter can be found here.

The equation can be solved using Kirchhoff's loop rule.

refers to the battery emf. represents the current through the circuit. indicates the voltmeter resistance and tag_5$ the internal resistance.

This is the expression for the potential difference in the voltmeter using Ohm's law.

represents the potential difference in the voltmeter.

The Kirchhoff loop rule states that the equation will be,

To find the current flowing through the circuit, rewrite the equation.

The potential difference in voltmeters is described as,

Substitute [katex]\varepsilon/E_v+r[/katex] to .

Ans:

The required potential change measured by the Voltmeter is .

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Unlike the idealized voltmeter, a real voltmeter has a resistance that is not infinitely large.