Chapter 10, Electrical Circuits Flashcards
What is Kirchhoff’s second law?
The sum of the e.m.f.s is equal to the sum of the p.d.s in a closed loop
What can Kirchhoff’s second law be broken down to? (Interpreted as)
The total energy transferred to the charges in a circuit is always equal to the total energy transferred from the charges as they move around the circuit.
How is current affected by components in a series circuit?
It isn’t, it is the same all the way round
What is the sum of the p.d. Across components in a circuit equal to?
The e.m.f. (Components with more resistance get a higher share of the voltage)
In a parallel circuit, how much of the current will a branch with twice the resistance of another branch receive?
Half of the current
How does Kirchhoff’s second law work in parallel circuits?
The sum of the e.m.f. Is equal to the sum of the p.d. of all the components in that closed loop (branch of the parallel circuit)
What does a power source need in order to output a high current?
A low internal resistance, such as a car battery
How is energy ‘lost’ in the cell of an electrical circuit?
Energy is ‘lost’ to heat as work has to be done by the charge carriers in the power source, for a chemical source, this is due to reactions between chemicals.
What is terminal p.d.?
The p.d. measured at the terminals of a power source
How does terminal p.d. differ from e.m.f.?
The terminal p.d. Is lower than the actual e.m.f. due to energy lost from internal resistance, these are called lost volts.
What is the equation for e.m.f. in terms of terminal p.d.?
Electromotive force = terminal p.d. + lost volts
How does an increase in current affect terminal p.d. and lost volts when the emf remains constant?
And increase in current means more charge carriers doing work in the cell which increases lost volts and decreasing terminal p.d.
What is the equation for lost volts?
V (Lost volts) = I (current) x r (internal resistance)
What’s the equation for emf from a power source (derived from e = v + lost volts)
emf = V (terminal p.d.) + I (current) x r (internal resistance) or emf = I (current) x (R (resistance) + r (internal resistance))
