Chapter 10: Electrical Circuits Flashcards
What is Kirchhoff’s First Law?
Kirchhoff’s first law dictates that all the current transmitted through a junction is equal to the current out of a junction in a closed loop
What is Kirchhoff’s Second Law?
Kirchhoff’s second law states that the sum of the electromotive forces is equal to the sum of the potential difference around a closed loop
How is E.M.F shared between multiple resistors?
If a circuit contains components with the same resistance, e.m.f is shared equally. If the components have different resistances, the component with the greater resistance has the greater proportion of e.m.f
What happens when a circuit contains two sources of e.m.f?
If the sources point in the same direction, they add together to provide a stronger e.m.f
If the sources point in opposite directions, the source with the stronger e.m.f will have to overcome the weaker one, reducing the e.m.f provided
How is current distributed in a parallel circuit?
The greater the resistance of a branch, the lower the current that passes through. This is because resistance and current is inversely proportional
How is e.m.f distributed across parallel branches?
E.M.F across each branch is equal to the power supply as they each create their own closed loop
When there is a parallel loop in a series circuit, voltage is equally shared across both branches
What is the proof for the equation of total resistance in series?
VT = V1 + V2 + …
IR T = IR1 + IR 2 + …
R T = R 1 + R 2
Current can be removed as it is equal across all components
What is the proof for the equation of total resistance in parallel?
IT = I1 + I2 + …
V/RT = V/R1 + V/R2 + …
1/RT = 1/R1 + 1/R2 + …
Voltage can be removed from the equation as voltage is equal across all branches in parallel
What is internal resistance?
Internal resistance is the resistance found within a power source. When there is a current in a power source, work has to be done by charges as they move through it
Why is work done in a chemical cell/ solar cell?
In a chemical cell, work done is due to reactions between chemicals
In a solar cell, it is the resistance of the materials
What is the relationship between EMF and voltage across terminals?
Voltage at the terminals of the power source are less than the actual e.m.f. because some energy from the e.m.f. dissipates as heat
What are lost volts?
Lost volts are volts that are not transferred around the circuit as they are transferred to the internal resistance
What is the formula for EMF?
EMF = Terminal PD + Lost Volts
What is the formula for lost volts?
Lost volts = I *** r
r is the internal resistance
