Conservaion Of Charge & Energy In A Circuit + Potential Dividers Flashcards
Is it correct that charge is conserved?
Yes
The amount of charge flowing into a junction is [……….] to the charge flowing out of that junction.
Equal
Define Current?
Rate of flow of charge
Because Current is Rate of Flow of charge and charge is the same when entering and exiting a junction what equation can we derive?
I1 = I2 + I3
What is Kirchhoffs 1st Law?
The total current entering a junction = the total current leaving it
Energy is [……..]
Conserved
What two variables must be equal in a closed loop for energy to be conserved ?
E.M.F and Potential Difference
What is Kirchhoffs 2nd Law?
The total E.M.F around a series circuit = the sum of the PD’s across each component
What is the Resistance equation for a Series Circuit?
R (total) = R1 + R2 + R3
Derive the equation R (total) = R1 + R2 + R3
1 - Current is the same at all points because there are no junctions in a series circuit
2 - E.M.F split between components (Kirchhoffs 2nd Law) e = V1 + V2 + V3
3 - V = IR so if I is constant
IR (total) = IR 1 + IR2 + IR3
4 - Cancel Out I gives R (total) = R1 + R2 + R3
What is the equation for resistors in parallel?
1 / R (total) = 1 / R1 + 1 / R2 + 1 / R3
How do you derive the equation for resistors in parallel? 1 / R (total) = 1 / R1 + 1 / R2 + 1 / R3
1 - Current is split at each junction so : I = I1 + I2 + I3
2 - PD is constant in a parallel circuit so the PD is the same
3 - V / R (total) = V / R1 + V / R2 + V / R3
4 V is constant so cancelling V Gives
1 / R (total) = 1 / R1 + 1 / R2 + 1 / R3
What do you use a Potential Divider for?
To get a fraction of a source voltage
What would the potential divider read if you had a 2 Ω resistor and a 3 Ω resistor?
- You would get 2/5 of the PD’s across the 2 Ω Resistor
- and 3/5 across the 3 Ω resistor
What is the Potential Divider Equation?
V (out) = ( R2 ) / ( R1 + R2 )
