27.11
Voltímetro
Un voltímetro es un dispositivo eléctrico que mide la diferencia de potencial o voltaje entre dos puntos. Se conecta en paralelo con el elemento del c…
En un circuito eléctrico, un voltímetro conectado en paralelo con el elemento del circuito mide la diferencia de potencial entre los dos puntos del elemento del circuito.
Un voltímetro ideal debe tener una resistencia infinita para que no extraiga corriente del circuito. Sin embargo, los voltímetros reales tienen una resistencia finita.
Es deseable tener un valor grande para la resistencia de modo que la conexión del voltímetro a un circuito no altere apreciablemente la diferencia de potencial medida.
Cualquier galvanómetro se puede convertir en un voltímetro agregando una resistencia limitadora de corriente en serie.
La diferencia de potencial requerida para la deflexión a escala completa solo para el galvanómetro es en milivoltios.
El rango del galvanómetro se puede aumentar conectando una resistencia de alto valor en serie con la bobina.
Esta configuración distribuye la diferencia de potencial total entre los dos componentes en serie. Como resultado, solo aparece una fracción de la diferencia de potencial total a través de la bobina.
A partir de esta expresión, se puede determinar el valor de la resistencia en serie requerida para diseñar un voltímetro con lectura a escala completa.
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Q1: Why is a voltmeter connected in parallel with a circuit element?
A voltmeter is connected in parallel because elements in parallel experience the same potential difference. This configuration allows the voltmeter to measure the voltage across the circuit element without being in series with the current path. Parallel connection ensures accurate measurement of the potential difference between two points.
Q2: What is the difference between an ideal and real voltmeter?
An ideal voltmeter has infinite resistance, so it draws no current from the circuit. Real voltmeters have finite resistance but should have high enough resistance to avoid significantly altering circuit currents. Inexpensive voltmeters have resistances around 10 megaohms, while high-precision voltmeters reach 10 gigaohms.
Q3: How can a galvanometer be converted into a voltmeter?
A galvanometer converts to a voltmeter by adding a high-value resistor in series with the coil. This series resistor limits current and extends the measurement range. The total potential difference distributes between the resistor and coil, so only a fraction appears across the galvanometer coil at full-scale deflection.
Q4: What role does the series resistor play in voltmeter design?
The series resistor in a voltmeter acts as a current-limiting component that extends the measurement range. It distributes the total potential difference between itself and the galvanometer coil. By calculating the appropriate series resistor value, designers can achieve full-scale deflection readings for specific voltage ranges.
Q5: Why do voltmeters need high resistance values?
High resistance in a voltmeter minimizes current draw from the circuit being measured. This prevents the voltmeter from appreciably altering the circuit's behavior or the measured potential difference. The higher the voltmeter's resistance, the less it disturbs the circuit and the more accurate the voltage measurement becomes.
Q6: What is electromyography and how does it use a voltmeter?
Electromyography is a medical diagnostic technique that uses a sensitive voltmeter to measure electrical activity in muscles. A fine needle with two electrodes is inserted into muscle tissue, and the voltmeter measures the potential difference between the electrodes. Physicians use these readings to diagnose neurological and neuromuscular diseases.
Q7: How does voltmeter resistance affect circuit measurements?
Voltmeter resistance directly impacts measurement accuracy. If resistance is too low, the voltmeter draws significant current and alters the circuit's behavior, leading to inaccurate readings. Sufficient resistance ensures the voltmeter measures the true potential difference without substantially changing the currents in the circuit being analyzed.