Circuits / Switches / Currents -TRUE FALSE QUESTIONS (Pic included)

[niravana21]

Circuits / Switches / Currents --TRUE FALSE QUESTIONS (Pic included)

Homework Statement

Homework Equations

The Attempt at a Solution

I really have no idea, on going about solving this as I don't have my book with me and the homework is due in a few hours. I'm sure if brief explanations are provided with your're reasoning, I will be able to understand the concept.

I realize this is not the way of the physics forum, but I really am desperate right now.

Hope you guys understand. Thanks in advance.

 

[sandy.bridge]

A current will develop in the circuit when the switch is closed. After the switch is opened, the same current is within the circuit, however, the total resistance of the circuit has changed.

When you calculate the total initial resistance, is it larger than the resistance if you were to assume the middle branch is an open circuit?

 

[lewando]

A current will develop in the circuit when the switch is closed. After the switch is opened, the same current is within the circuit, however, the total resistance of the circuit has changed.

After the switch is opened, a different current will flow, because the resistance has changed.

 

[niravana21]

so if I'm understanding correctly, which I'm not too sure, would it go like this?

8.True
9.False
10.False
11. True
12. True

again, it would be helpful if you can tell me why I'm incorrect rather than provide the right answer. Thanks members!

 

[lewando]

If you would like someone to tell you why you are incorrect, you should at least explain why you think you are correct.

 

[niravana21]

fair enough :) I don't even know if some of my reasonings are valid haha

8. The total power that is dissipated should be conserved so True
9. (not sure at all, just guessed)
10. Voltage stays the same though out the circuit so False
11. True because closing the switch causes current to flow though and increases resistance?
12. true because uhh it sounds true :) (not sure either way)

 

[lewando]

8. The total power that is dissipated should be conserved so True

Sorry, this is not so. Energy may be conserved, power is another animal. The resistive load on the voltage supply changes, therefore the current changes. What is the equivalent resistance before the switch is opened? After it is opened? Assume the battery is 1.5V. What is the current (provided by the battery) before and after switch is opened? Use P=VI, P=VI, P=V²/R or P=I²R to compare power dissipated in each circuit.

9. (not sure at all, just guessed)

After the switch is opened R2 is just dangling out there--how can current go through it?

10. Voltage stays the same though out the circuit so False

When you figure out what the currents are (before/after switch opened) you will be able to answer this.

11. True because closing the switch causes current to flow though and increases resistance?

When you figure out the equivalent resistance of the circuits (before/after switch opened) you will be able to answer this.

12. true because uhh it sounds true :) (not sure either way)

When you figure out the current of circuits (before/after switch opened) you will be able to answer this.