Current and Voltage of Elements of a Circuit with a Solenoid.

Ended up figuring out how to solve this problem. I just was not expecting certain parts of the results which lead me to believe I did it wrong.

Homework Statement

Voltage of battery is 5V
Resistors are 5 Ohms
The solenoid has no internal resistance

1.Need to find V_2 before switch is opened
2.The current through the solenoid right after the switch has been opened.
3. The current through R_2 and R_1 right after the switch has been opened.
4. Voltage across R_1 right after the switch has been opened.
5. Voltage across R_1 if it was 5 Mohms right after the switch has been opened.

Homework Equations

V=IR
Kirchhoff's Loop Rule

That a solenoid will want to resist any change in current.

The Attempt at a Solution

1. The voltage across R_2 will be 5V because the loop that consists of the switch and resistor has to have a voltage drop of 5 V and the resistor is the only element with a voltage drop on that loop.

2. The current through the solenoid right after the switch is open will be 1 A as the solenoid will want to keep the same current as before.

3. 1 A as the current will be same as the solenoid.

4. The voltage drop across both of the resistors will be 5 V. The solenoid will add additional voltage to create the greater voltage.

5. 5*10^6 V as the current will still be 1 A.

I know I probably have flawed logic in here somewhere though I just do not know exactly how a solenoid will effect this circuit after the switch is thrown.

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rude man
Homework Helper
Gold Member
Are you interested in these various V's and i's just after the switch is opened, or for all time after the switch is opened?

Just after the switch has been opened. Sorry thought I put that in the questions but I must of missed putting that there.

rude man
Homework Helper
Gold Member
Just after the switch has been opened. Sorry thought I put that in the questions but I must of missed putting that there.
Everything is correct. Congrats!

Yeah I ended up getting the answers back and I got a happy suprise when I saw that I was correct. I guess thats why they put the question in the post lab, to show how solenoids can do this.