In measuring a voltage, a voltmeter uses some current from the circuit. Conseque

Question

In measuring a voltage, a voltmeter uses some current from the circuit. Consequently, the voltage measured is only an approximation to the voltage present when the voltmeter is not connected. Consider a circuit consisting of two 2300 ohm resistors connected in a series across a 70.0-V battery. (a) Find the voltage across one of the resistors. (b) A voltmeter has a full-scale deflection of 5.14 mA. Determine the voltage that this voltmeter registers when it is connected across the resistor that is used in part (a).

Explanation / Answer

Net resistance = 2300 +2300 = 4600 ohms

Net current = V/R = 70/4600 = 0.0152 A

Across one resistor voltage = IR = 0.0152*2300 = 35V

Current passing through resistor when voltmeter is connected = 0.0152-0.00514 = 0.01006 A
So reading recorded = V = IR = 0.01006*2300 = 23.138 V

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