Chapter 10: Electrical Circuits Flashcards
What is Kirchoff’s Second Law, and what is conserved?
Kirchoff’s Second Law states that within a circuit, the sum of the Electromotive Force (e.m.f.) is equal to the sum of the Potential Difference (p.d.) within a closed loop. In Kirchoff’s Second Law, energy is conserved
What is a series circuit?
A series circuit is a circuit where the current only has a single path it can travel in, consisting of a single loop.
What is a parallel circuit?
A parallel circuit is a circuit where current has more than one path it can travel in consisting of multiple loops.
The amount of charge that flows into each path depends on the total resistance within that path, and each branch / loop within a circuit can be considered as a separate circuit / loop.
How do you calculate the total resistance within a series circuit?
In a series circuit, you add the total resistance of each component together to find the total resistance of the circuit:
R = R1 + R2 + R3…
How do you calculate the total resistance within a parallel circuit?
In a parallel circuit, you add the reciprocal resistance of the resistances in each loop together, and do the reciprocal of the answer to calculate the resistance.
1 / R = 1 / R1 + 1 / R2 + 1 / R3…
*You can do this to simplify resistances for parallel circuits within another circuit.
What are the 4 Equations and laws required to analyse circuits?
When analysing circuits, the equations needed are:
I = Q / t, V = W / Q, P = IV and V = IR
Laws needed to solve circuits are Kirchoff’s First and Second laws.
What is internal resistance?
Internal resistance is the resistance of an emf source, which causes a loss of energy in the form of heat within the emf source in the form of heat when work is done on the emf source. Eg: A battery.
What is terminal p.d.?
Terminal p.d. is defined as the p.d. across an electrical power source.
What are ‘lost volts’?
Lost Volts is the work done per unit charge that is converted from electrical energy into heat due to the internal resistance of an emf source.
What is the equation that links the emf of a circuit, current, resistance and internal resistance?
The equation that links emf, current, resistance and total resistance is:
e.m.f. = IR + Ir
OR
e.m.f. = I (R + r)
What is the equation that links emf, terminal p.d. and lost volts?
The equation that links e.m.f., terminal p.d. and lost volts is:
e.m.f. = Terminal p.d. + lost volts
What is the gradient and equation of a V-I Graph of an emf source with internal resistance?
The gradient of a V-I Graph for a component with an internal resistance is -r (negative resistance, due to negative gradient), and the equation of this graph is:
V = -r I + emf
y = m x + c
What is a Potential Divider?
A Potential Divider is a type of electrical circuit used to divide the potential difference across two or more components within a circuit in order to produce a specific p.d. output. This is mainly done using variable resistors.
What is the Ratio of resistances for two components?
The ratio of resistances for two or more components is:
V1 / V2 = R1 / R2
*You can rearrange to find a missing value for any components.
What is the potential divider equation?
The potential divider equation is:
V (out) = ( R2 / (R1 + R2) ) x V (in)
*Where R2 is the Resistance of the Resistor where the output is connected at.
