Electricity: voltage calculation in serial

In summary, the voltmeter gives a value of 150V. The Attempt at a Solution found that if I have only one equation, I can try to create a system of linear equations.
  • #1
Epoch
24
0

Homework Statement


Calculate the voltage U.
The voltmeter gives a value of 80V.
exercise.png


The Attempt at a Solution


[/B]
3RI + 4RI - U = -80
How can I create a System of Linear equations if I have only one equation?
Do I miss something?

My answer sheet says U = 150V.
 
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  • #2
What is 'R'? Is it a variable, or does it represent "resistor"? I guess it really doesn't matter. If it is a variable, the R's should cancel out. You know that the voltage across the 2 inside resistors is 80 V, so you should be able to come up with a second equation for that.
 
  • #3
Epoch said:

Homework Statement


Calculate the voltage U.
The voltmeter gives a value of 80V.
View attachment 194684

The Attempt at a Solution


[/B]
3RI + 4RI - U = -80
How can I create a System of Linear equations if I have only one equation?
Do I miss something?

My answer sheet says U = 150V.

Let I be the current through the circuit. The V to the drop at 2R and 6R, so
2RI + 6RI = 80
8RI = 80
RI = 10

For the whole circuit,
U - 3RI - 2RI - 6RI - 4RI = 0

Try to take it from there!
 
  • #4
D Nguyen said:
Let I be the current through the circuit. The V to the drop at 2R and 6R, so
2RI + 6RI = 80
8RI = 80
RI = 10

For the whole circuit,
U - 3RI - 2RI - 6RI - 4RI = 0

Try to take it from there!

Thanks, I got it.
 
  • #5
D Nguyen said:
Let I be the current through the circuit. The V to the drop at 2R and 6R, so
2RI + 6RI = 80
8RI = 80
RI = 10

For the whole circuit,
U - 3RI - 2RI - 6RI - 4RI = 0

Try to take it from there!

RI = 10
U - 3RI - 2RI - 6RI - 4RI = 0
U - 3*10 - 2*10 - 6*10 - 4*10 = 0
U - 30 - 20 - 60 - 40 = 0
U - 150 =0
U = 150V

I found it, thanks for your help.
 

FAQ: Electricity: voltage calculation in serial

What is voltage?

Voltage is a measure of the potential difference in an electric circuit. It is often referred to as the force that pushes electrons through a conductor.

How is voltage calculated in a series circuit?

In a series circuit, the total voltage is equal to the sum of the individual voltages in the circuit. This means that you simply add up all the voltage sources in the circuit.

Why is voltage important in electricity?

Voltage is important because it is what drives the flow of electricity through a circuit. Without voltage, there would be no electrical current and no way to power electronic devices.

What is the unit of measurement for voltage?

Voltage is measured in volts (V), which is named after Italian physicist Alessandro Volta who invented the first battery.

Can voltage be negative?

Yes, voltage can be negative. This occurs when the polarity of the voltage source is reversed, causing the electrons to flow in the opposite direction in the circuit. A negative voltage can still be used to power devices, as long as it is within the appropriate range for the device.

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