23.3- CHARGING AND DISCHARGING A CAPACITOR THROUGH A FIXED RESISTOR Flashcards
When a capacitor discharged through a fixed resistor, what happens to the discharge current?
decreases gradually to zero
When a capacitor is discharged through a resistor, what does the current decrease gradually?
as pd across capacitor decreases as it loses charge
as resistor connected directly to capacitor, resistor current decreases as pd decreases
How does current and charge (and pd) decrease when a capacitor discharges?
exponentially
What does ΔQ/Q equal?
ΔQ/Q = - Δt/CR
What is the equation for Q?
Q = Q0 e –t/RC
Q0 - initial charge
e - exponential function
What is the quantity of RC called?
time constant
What is the unit of RC?
seconds
Why is an oscilloscope used when investigating capacitor discharge?
as it has a very high resistance so discharge current from capacitor passes only through fixed resistor
What is the oscilloscope used to measure when investigating capacitor discharge?
capacitor pd at regular intervals
What can be used instead of a oscilloscope to measure to capacitor pd at regular intervals? (investigating capacitor discharge)
data logger or digital voltmeter
When a capacitor is charged by connecting it to a source of constant pd, what happens to the charging current and why? (charging a capacitor through a fixed resistor)
charging current decreases as capacitor charge + pd increase
When a capacitor is fully charged, what is its pd and current like? (charging a capacitor through a fixed resistor)
pd equal to source pd, and current zero as no more charge flows in circuit
