# Calculate the voltmeter reading for this circuit with 2 sources and 2 resistors

• songoku
In summary, the conversation discusses the voltmeter reading for a circuit with a current of 2 A and a voltage of 10 V. While the initial calculation suggests a reading of 8 V, the correct answer is 12 V based on the values for current returning to cell A and B, and current entering the voltmeter. The final calculation involves using Ohm's Law to determine the resistance and ultimately, the voltmeter reading.
songoku
Homework Statement
Relevant Equations
V = I.R

I find the current first, which is 2 A. Then the voltmeter reading would be 10 V - 1 x 2 = 8 V.

But the answer is 12 V.
I don't understand why it should be 10 + 1 x 2 = 12 V

Thanks

I agree with your answer. It obviously cannot be more than 10V.

songoku and MatinSAR
Thank you very much haruspex

Yes, I agree, 8V is correct.

songoku
Current returning to cell A = x
Current returning to cell B = y
Current entering the voltmeter = z

10- 1*x=0
4- 2*y = 0
z = y + x

X=10
Y=2
Z=12

U=RI

1/R=1/1+1/2
1/R=1,5
R=2/3

U = (2/3)*12 = 8

Daniel Weng
Welcome to PF, @erpelkon

erpelkon said:
Current returning to cell A = x
Current returning to cell B = y
Current entering the voltmeter = z

10- 1*x=0
4- 2*y = 0
z = y + x

X=10
Y=2
Z=12

U=RI

1/R=1/1+1/2
1/R=1,5
R=2/3

U = (2/3)*12 = 8

It is okay to offer alternate solutions to old schoolwork threads where the OP has already solved the problem. Please just keep in mind that in active threads, the OP must do the bulk of the work. We cannot offer solutions to them until after they have solved their schoolwork problem. Thanks.

MatinSAR and erpelkon

## How do I approach solving for the voltmeter reading in a circuit with two sources and two resistors?

To solve for the voltmeter reading, you should first identify the configuration of the circuit (series, parallel, or a combination). Then, apply Kirchhoff's Voltage Law (KVL) or Kirchhoff's Current Law (KCL) as needed. Calculate the voltage drops across each resistor using Ohm's law, and then determine the potential difference where the voltmeter is connected.

## What is Kirchhoff's Voltage Law (KVL) and how is it applied in this context?

Kirchhoff's Voltage Law states that the sum of all voltages around a closed loop in a circuit must equal zero. In this context, you would write equations that sum the voltage contributions from both sources and the voltage drops across the resistors, then solve for the unknown voltages.

## How do I handle circuits with both series and parallel components?

For circuits with both series and parallel components, you need to break down the circuit into simpler parts. Calculate the equivalent resistance for parallel parts first, then treat the circuit as a series circuit. Use Ohm's law and KVL/KCL to find the voltages and currents in each part of the circuit.

## What role do the resistors play in determining the voltmeter reading?

Resistors determine how the voltage from the sources is divided across the circuit. The voltage drop across each resistor can be calculated using Ohm's law (V = IR). The voltmeter reading will depend on these voltage drops and their arrangement in the circuit.

## How do I account for the presence of two voltage sources in the circuit?

When there are two voltage sources, you need to consider their relative polarities and magnitudes. If they are in series, their voltages add algebraically. If they are in parallel, you need to ensure they have the same voltage and consider their combined effect on the circuit. Use superposition theorem if necessary to analyze the contribution of each source separately.

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