5.3 - Circuits & The Potential Divider Flashcards
What is the combined resistance of resistors in series?
RT = R1 + R2 + R3…
What is the combined resistance of resistors in parallel?
1/RT = 1/R1 + 1/R2 + 1/R3…
What is the current of the components in a series circuit?
They are all the same current.
What is the current of the components in a parallel circuit?
Depends on the branch.
The amount of current in each depends on RT in the branch.
IT into junction = IT out of junction
What is Kirchhoff’s 1st law?
The total current that enters a junction is equal to the total current that leaves the junction.
What is the voltage flowing through components in a series circuit?
The e.m.f of the power supply is shared amongst all the components in different amounts depending on their resistance.
What is the voltage flowing through components in a parallel circuit?
The voltage of all the components in each branch is equal to the e.m.f of the power supply.
Is charge conserved in a circuit?
It is never used up or lost in a circuit so yes.
What is a junction?
A point where at least 3 circuit paths meet.
What is a branch.
A path connecting 2 junctions.
What is Kirchhoff’s first law in numbers?
I = I1 + I2 + I3
What is Kirchhoff’s 2nd law?
The total e.m.f in a closed circuit equals the sum of the potential differences across each component.
What are the equations for power?
P = E/t
P = IV
P = I²R
P = V²/R
What can the formula for energy be written as?
E = VIt
(voltage, current, time)
What are potential dividers?
A circuit with several resistors in series connected across a voltage source, used to produce a required fraction of the source potential difference, which remains constant.
What are the 2 main purposes of potential dividers?
- To provide a variable potential difference to enable a specific potential difference to be chosen
- To split the potential difference of a power source between 2 or more components
What is the potential divider equation?
Vout = (R2 / R1 + R2)Vin
What is an LDR?
A sensory resistor (like a thermistor) which stands for light dependent resistor.
What is the symbol for a LDR?
A rectangle with 2 arrows pointing at it.
With LDR, what is the relationship between light intensity and resistance?
The higher the light intensity, the lower the resistance.
The lower the light intensity, the higher the resistance.
What is the relationship between Vout from a resistor in a potential divider circuit?
The potential difference is proportional to its resistance.
LDR/thermistor’s resistance decreases, p.d decreases (vice verse)
