Yr 12 - Electrical Circuits Flashcards
Kirchhoffs Second Law
∑ε (EMF) = ∑V (Potential Difference) in any closed circuit
Series, Parallel & Series-Parallel circuit.
Series - One path
Parallel - 2 or more paths
Series-Parallel - Some components connected in series, some connected in parallel.
How does the current vary across different types of circuit?
Series - Same throughout
Parallel - Splits at junctions
Equation linking resistance and PD of 2 consecutive components
V1/V2 = R1/R2
Equation for EMF
- What does IR calculate?
ε = V + IR
OR
ε = I (R+r)
IR = Lost volts
What is Internal Resistance?
Work being done by charge on source of EMF
What is Terminal Voltage? (Terminal PD)
= EMF - Lost Volts
- PD between the terminals of a power source when connected in complete circuit.
What is lost volts?
Difference between EMF & terminal PD due to internal resistance.
How to measure EMF?
Connect Voltmeter in parallel over battery.
- Disconnect rest of circuit so that EMF measured and not Terminal PD.
What is load resistance?
Total resistance outside the power source.
What is a potential divider.
A circuit where output PD can be varied.
- As one components resistance decreases, the change in R is added the other component/s.
Equation for the V out in a potential divider.
V Out = V In (R2 / R1 + R2)
How to these components change due to a heat increase?
- Filament Lamp
- Thermistor
- LDR
Filament Lamp - Resistance increases
Thermistor - Resistance Decreases
LDR - Resistance decreases (Light intensity increase)
Terminal PD
PD across source of EMF when connected to full circuit.
Potentiometer
A manually adjustable variable resistor with 3 terminals.
