Engineering Combined Circuit Total Resistance

[Infecthead]

Homework Statement

OK so I have calculated the total resistance for the series and parallel part of the circuit. Now I just need help with the total

Homework Equations

Experimental Results:
Bulb 1: Volts = 3 Current = 0.46 Resistance1 = 3 ÷ 0.46 = 6.5
Bulb 2: Volts = 3 Current = 0.46 Resistance2 = 3 ÷ 0.46 = 6.5
Bulb 3: Volts = 5.5 Current = 0.46 Resistance3 = 5.5 ÷ 0.46 = 11.9
Total Resistance(series) = Resistance1 + Resistance2 = 6.5 + 6.5 = 13
Total Resistance(parallel) = 1 ÷ (1 ÷ R1) + (1 ÷ R2) + (1 ÷ R3) = 6.7

What is the equation to find out the Total Resistance of the whole circuit.

 

[Dadface]

Can you show the circuit?

 

[Infecthead]

[PLAIN]http://img31.imageshack.us/img31/7056/circut.png

Theres the 3 lighbulbs, on the right is the switch and the top part is the power pack.

Thanks for the quick response

 

[anthonuc]

Are the three bulbs the only resistances in the circuit?

Then all you would have to do is find the total resistance of the lightbulbs which I believe you did. The two in series and then that in parallel with the other bulb should be the total resistance assuming the battery's resistance to be negligent.

 

[Zryn]

If the circuit is set up like that, then the sum of the voltages across Bulb 1 & 2 (series branch) should be the same as Bulb 3 (parallel branch).

3 + 3 != 5.5 (close enough is good enough maybe?)

If the current you measure through each branch is 0.46A then the resistance of each branch is equal and the current is being split equally between branches.

6.5 + 6.5 != 11.9 (close enough is good enough again?)

You can remember that two equal resistances in series will double the value, two equal resistances in parallel will halve the value. Math is always better though.