Failed Device - What Circuit Fault is Indicated and Where?

In summary, one of the devices in the circuit has shorted out, causing a loss of current and a voltage drop across the other devices.
  • #1
mjcino
2
0

Homework Statement


Four devices are connected in series across a voltage source of 120V. The total circuit current is 4.5A. One device fails to operate. The voltage across each of the other devices is 40V. What circuit fault is indicated and where?


Homework Equations


E=IR
I=E/R
R=E/I
et al.


The Attempt at a Solution


I'm afraid I'm not really sure what the instructor is looking for here. It seems clear to me that one of the devices has shorted out. I wrote for my answer, "One of the devices has shorted out - its resistance has become 0 ohms." That sounds like the circuit fault to me, but where . . . ? Am I missing something here?
 
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  • #2
I think you have it right.

If there were only resistive devices present, (ie no inductors or capacitors) the total resistance is 26.66 ohms ( 120 V / 4.5 Amps = 26.66 ohms.) Each device has 40 volts across it and 4.5 amps through it, so each has a resistance of 8.89 ohms. ( 40 V / 4.5 = 8.89 ohms).

The main clue is that the 3 remaining devices have a total of 120 volts across them, so there can't be any voltage across the remaining device, whatever it was.
Maybe this indicates a fault. Maybe not. You would have to know what the other device was.

Unless you are told that this was a fault, the 4th device could be a switch. It is quite normal for a switch to be short-circuited when it is turned on.
 
  • #3
mjcino said:

Homework Statement


Four devices are connected in series across a voltage source of 120V. The total circuit current is 4.5A. One device fails to operate. The voltage across each of the other devices is 40V. What circuit fault is indicated and where?


Homework Equations


E=IR
I=E/R
R=E/I
et al.


The Attempt at a Solution


I'm afraid I'm not really sure what the instructor is looking for here. It seems clear to me that one of the devices has shorted out. I wrote for my answer, "One of the devices has shorted out - its resistance has become 0 ohms." That sounds like the circuit fault to me, but where . . . ? Am I missing something here?

I agree with v6kro. The only thing I can add is that it is common in talking about failures of electronic devices to classify them as failed short or failed open. And it is also common for a device to first fail short, and then fail open as it dissipates too much power and overheats to the point of melting and blowing open.
 

1. What is a failed device?

A failed device refers to an electronic component or circuit that is no longer functioning as intended. This can be due to various reasons such as wear and tear, manufacturing defects, or external factors like power surges.

2. How can I determine the circuit fault for a failed device?

The circuit fault for a failed device can be determined through a process called fault-finding. This involves testing the different components and connections in the circuit to identify the specific fault that is causing the device to fail.

3. What does a circuit fault indicate?

A circuit fault indicates that there is a problem with the flow of electricity in a circuit. This can be caused by a variety of issues such as a broken wire, a faulty component, or a short circuit. Identifying the circuit fault is crucial in order to fix the failed device.

4. Where can I find information about the circuit fault for a failed device?

The circuit fault for a failed device can be found in the device's user manual or technical documentation. It can also be identified through testing and troubleshooting the device's circuit using specialized equipment and knowledge.

5. How can I prevent circuit faults that lead to failed devices?

To prevent circuit faults that lead to failed devices, it is important to regularly maintain and inspect electronic devices. This can help identify any potential issues before they cause a failure. In addition, using surge protectors and following proper usage guidelines can also help prevent circuit faults and prolong the lifespan of electronic devices.

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