Understanding High Electrical Resistance in Circuits

The question asks us to identify an electrical component characterized by high electrical resistance. This high resistance is crucial because it ensures that the component draws only a small amount of electrical current from the circuit. Consequently, the power it consumes is also minimal. Let's examine the function and characteristics of each option provided:

Analyzing Electrical Components

• Ammeters: These instruments are designed to measure the electrical current flowing through a point in a circuit. To perform this function accurately without significantly altering the current being measured, ammeters must have a very low internal resistance. They are connected in series with the circuit path.
• Voltmeters: These instruments are used to measure the electrical potential difference (voltage) across two points in a circuit, typically across a component. To ensure they draw negligible current from the circuit (and thus not affect the voltage being measured), voltmeters are designed to have a very high internal resistance. According to Ohm's Law, the current ($I$) drawn by the voltmeter is given by $I = V/R$, where $V$ is the voltage across it and $R$ is its resistance. A high $R$ leads to a very small $I$. The power absorbed by the voltmeter is $P = V \times I = V^2/R$. A high resistance $R$ ensures minimal power absorption ($P$). Voltmeters are connected in parallel across the component whose voltage is being measured.
• Transformers: Transformers are devices used to transfer electrical energy between two or more circuits through electromagnetic induction. Their primary function is voltage and current transformation. While they have internal resistances in their windings, having inherently high electrical resistance is not their defining operational characteristic in the context of minimizing current draw for measurement purposes.
• Ohmmeters: These are instruments used to directly measure electrical resistance. They are typically connected directly across the component whose resistance is to be measured (with the circuit powered off). While they involve resistance principles, their defining characteristic isn't operating with high resistance *within* an active circuit to draw minimal current like a voltmeter.

Conclusion on Resistance and Current Draw

Based on the analysis, the device designed specifically to have high electrical resistance to ensure it draws a minimal current and absorbs little power when connected in parallel is the voltmeter. This property is essential for accurate voltage measurements.