Voltage and current measuring meters affect the circuit they arc measuring to so
ID: 1443861 • Letter: V
Question
Voltage and current measuring meters affect the circuit they arc measuring to some extent Voltmeter is an instrument for measuring potential difference (voltage between two points) Voltmeters should always be connected in parallel with the circuit element. Any current passing through voltmeters affect the overall current and voltage measurement in the circuit. Ideally, a perfect voltmeter should have an infinite internal resistance, so that no current pass through it. To understand how the internal resistance of voltmeters affect voltage measurements, consider the following circuit. R_1 =R_2 250MH and V 24 V Case II: Now connect a voltmeter with internal resistance (lead-to-lcad resistance) Rv - 10 Mil in parallel with R_2. It is like having R_2 in parallel with Rv. The voltmeter has greatly affected the voltage drop across R_2, this is because it internal resistance is small. For the voltmeter to have no effect on voltage measurement it needs to have very high resistance.Explanation / Answer
1) Here, V1 = 24/2 = 12 V
2) V2 = 24/2 = 12 V
3) Reff = 10 * 250/(10 + 250)
= 9.615 megaohm
4) Reff is smaller than R2
5) voltage drop across Reff = Veff = ((24)/(250 + 9.615)) * 9.615
= 0.888 V
6) Veff is very less than V2 .
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