Chapter 23 Flashcards
What is Kirchoff’s junction law
it describes how the total current of a junction must be conserved so I(in)=I(out)
if a charged particle moves around a closed loop and to its starting point, what is the change in the electric potential energy
the net change in the electric potential around a loop is zero
what is kirchhoff’s loop law
it says that the sum of the potential differences around a circuit is zero
what is the voltage drop formula at a resistor
V=-IR
What is the ∆V in a battery that has a current that flows from negative to positive?
it is ∆V=+ε
What is the ∆V in a battery that has a current that flows from positive to negative?
is is ∆V= -ε
For resistors what happens to the potential difference
the current flows from positive to negative, so the ∆Vr is always negative
the potential decreases along the direction of current and the charge flows downhill, we call this a voltage drop
what is a battery a source of? what is it not a source of?
it is a source of potential difference, it is not a source of current
what does the amount of current in a circuit depend on?
it depends on the battery emf and the resistance of the circuit attached to the battery
if you have a single lightbulb in a circuit, and two lightbulbs in another circuit with the same conditions, which bulb glows brighter?
the single lightbulb provides less resistance so it glows brighter
what are the key features of two bulbs connected in parallel?
they have the same ∆V, lower overall resistance, and glow brighter than series bulbs
What are the key features of bulbs in a series
they have the same current, higher resistance, and generally glow dimmer than bulbs in parallel
how must an ammeter be placed in a circuit in order to measure the current in a element?
it must be placed in series
the equivalent resistance of several resistors in parallel is
less than any single resistor in the group
when we add two light bulbs to a circuit, how does the battery respond?
it provides 2x the current to power them both equally
what is the assumption about the resistance in an ideal ammeter
we assume it is zero
where do we place a voltmeter to measure potential differences in a circuit
we place it in parallel with what we are trying to measure
what assumption do we make about an ideal voltmeter in regards to resistance
we assume it has infinite resistance so that current does not flow through it
when a capacitor is connected to a battery, what occurs?
the charge will flow to the capacitor until its potential difference equals the emf of the battery, when it is charged, there will be no further current
parallel capacitors have the same what?
they have the same ∆V
what is the total charge on a circuit with parallel capacitors
it is the sum of the individual charges from the capacitors
what is the charge of two capacitors in a series
they have the same charge
what are RC circuits
they are circuits that contain resistors and capacitors
what determines the time it takes for a capacitor to charge or discharge
the values of the resistance and the capacitance
what happens to the current when we add a capacitor to a resistor circuit?
the current varies with time
what happens to a charged capacitor when a switch is closed
the charge separation in the capacitor produces a potential difference that causes a current, but as the current flows, the capacitor is discharged so the potential difference and current decrease
in what fashion do current and voltage decrease in a capacitor?
they decrease by exponential decay
what value characterizes exponential decay in a RC circuit
the time constant τ
a large time constant τ indicates what
it implies a slow decay
a small time constant τ indicates what
a rapid decay
when a uncharged capacitor is connected to a battery, what happens
the current from the battery will charge the capacitor until ∆Vc= emf
