10.1 - 10.6 Flashcards
what is Kirchhoff’s first law
the current entering a junction equals the current leaving a junction. it’s the conservation of charge
what is Kirchhoff’s second law
the sum of the E.M.F’s equals the sum of the P.d’s in a closed loop. it’s the conservation of energy
how do current and P.d change in series and parallel circuits
Series:
current stays the same
P.d shared across components
parallel:
Current is shared across paths
P.D stays the same
how can the relationship between resistors in series be derived?
from Kirchhoff’s second law V(total) = V1 + V2.
V=IR so this can be re-written IR(total)= IR1 + IR2
from Kirchhoff’s first law we know I is constant so R(total) = R1 + R2
how can the relationship between resistors in parallel be derived?
From Kirchhoff’s first law I(total)= I1 + I2
this can be re-written V/R(total) = V/R1 + V/R2
from Kirchhoff’s second law we know V is constant so 1/R(total) = 1/R1 + 1/R2
what is current
the rate of flow of charge
what is the potential difference
the energy transferred between two points from electrical energy to other forms per unit charge
what causes internal resistance
the resistance of a source of E.M.F causing a loss in energy as charge passes through the source
why are some volts lost causing the P.d to be lower than the EMF of a cell
internal resistance causes an energy loss so not all the energy transferred to charge is available for the circuit
how does changing the current effect the voltage loss due to internal resistance
it is increased. this is because a higher current means more charge’s travel through the cell per second and so more work is done by the charge increasing the voltage loss.
who can the emf be measured
us a high resistance voltmetre to measure the P.d across the terminals when there is no current flowing through the circuit
what is a potential divider circuit
a circuit designed to divide the P.d across two or more components in order to produce a specific output
what is a potentiometer
a component with three terminals and a sliding contact used to vary the P.d across two of the terminals
