Physics #6 Flashcards
current is considered the flow of _____ charge even though _____ are actually moving
positive charge
negative
compare metallic and electrolytic conductivity
metallic: solid metals and molten forms of salts
electrolytic: in solutions
conductance
reciprocal of resistance
metallic conductivity
sea of electrons flowing all throughout the metallic mass.
electrolytic conductivity
depends on the strength of a solution (concentration)
what is the formal definition of current
the amount of charge passing through a conductor per unit time.
the direction of current is ______ the direction of electron flow
opposite
compare direct current (DC) and alternating current (AC)
direct current: charge flows in one direction only
alternating current: the flow of charge changes periodically.
Kirchhoff’s Junction Rule
at any point or junction, the sum of currents directed into that point equals the sum of currents directed away from that point
electromotive force vs. voltage
voltage: the potential difference between two points
emf: the potential difference of the voltage source for a circuit
does electrical current follow the continuity equation that fluids follow?
no
most conductors have ____ resistance at higher temperatures
greater
superconductors
when they are cooled to very low temperatures, the resistivity of the material drops to 0.
the rate at which energy is dissipated by a resistor is the ____ of the resistor
power
why is resistance decreased when resistors are added in parallel
more pathways, greater surface area.
when n identical resistors are wired in parallel, the total resistance is given by ____
R/n
In parallel, when a resistor is added, the overall resistance _____
decreases
The internal resistance of a battery will ____ the amount of current it can provide.
decrease
capacitance
the ratio of the magnitude of the charge stored on one plate to the potential difference (voltage) across the capacitor
how much is a picofarad?
10^-12 farads
the dielectric constant of a material is a measure of its ____
insulating ability
can a dielectric material decrease the capacitance?
no
what happens when a dielectric material is placed in an isolated, charged capacitor that is disconnected from any circuit?
decrease in voltage but increase in capacitance
charge stays the same
what happens when a dielectric material is placed in a charged capacitor within a circuit that is still connected to a voltage source?
the charge on the capacitor increases and the capacitance increases.
voltage stays the same
ammeter
used to measure the current at some point within a circuit
placed in series, no voltage drop and no resistance
requires a circuit to be active
voltmeter
requires a circuit to be active
measures a voltage drop
wired in parallel
infinite resistance (current will never go its way)
ohmmeter
does not require a circuit to be active
measures resistance
often have their own battery of known voltage
