The resistor and voltmeter were connected in parallel and connected to an ideal voltage source.
The resistor and voltmeter were connected in parallel and connected to an ideal voltage source. The voltmeter showed a voltage of 10 V. Then the resistor and voltmeter were connected in series and connected to the same source. This time the reading of the voltmeter was 6 V. Find the ratio of the resistances of the resistor and the voltmeter.
RU is the resistance of the voltmeter.
R1 is the resistance of the resistor.
Ohm’s law:
U = I * R.
1) 6V dropped on the voltmeter, we get the ratio:
6 = I * RU.
Let’s calculate the current in the voltmeter:
I = RU / 6.
2) Source voltage – 10V. This voltage is applied across the voltmeter and resistor.
This means that the resistor dropped 10 – 6 = 4V. Let’s calculate the current in the resistor:
4 = I * R1.
I = R1 / 4.
3) When connected in series, the current in all sections of the circuit is the same. Let’s equate the currents:
RU / 6 = R1 / 4.
RU = (6 * R1) / 4.
RU = 1.5 * R1.
The resistance of the voltmeter is 1.5 times greater.