A 20mV voltmeter of resistance 10^3ohm is to be converted into, (i) a voltmeter reading up to 5 V, (ii) an ammeter reading up to 2A. How can it be done? Circuit diagram for both essential.
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Voltmeters typically measures the current and calibrated in terms of Voltage.
Your Volt meter Full scale range is 15 V
Internal Resistance = 1000 Ohms
Therefore, the current flow is 15/1000 = 0.015 Amp 15 mA
If the Voltmeter needs to measure 150Volts then as, it is the current flow is 150/1000 = 0.15A = 150 mA
Now, this excess current 150 -15 = 135 mA is to be made to be reduced to make 150–15= 135 Volts dropped by sing additional Volts
Therefore add a resistor in series that will drop this 135 Volts
135/15 mA = 9000 Ohms. = 9 K Ohms. This resistor is to be placed in series with the meter.
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