Define exponential decay in the context of a discharging capacitor.

Exponential decay means the rate at which the current, p.d. or charge decreases is proportional to the amount of current, p.d. or charge remaining.

How does the current behave at the start of a capacitor's discharge, and how does it change over time?

The current is large at the start (in the opposite direction to when it was charging) and gradually falls to zero .

How does increasing the resistance in a discharge circuit affect the rate at which a capacitor discharges?

A higher resistance means the current decreases and charge flows from the plates more slowly , so the capacitor takes longer to discharge (a lower resistance discharges the capacitor faster).

During discharge, in which direction do electrons flow between the capacitor plates?

Electrons flow from the negative plate to the positive plate until there are equal numbers of charge on each plate.

True or False? During discharge, the current flows in the same direction as it did during charging.

False. During discharge, the current flows in the opposite direction to the current during charging.

The graphs of current, potential difference and charge against time during capacitor discharge are all .......... in shape.

The graphs of current, potential difference and charge against time during capacitor discharge are all identical in shape.

What effect does a larger time constant have on the rate of capacitor discharge?

The larger the time constant, the slower the current, charge or p.d. falls during discharge.

How is the natural logarithm, ln( y ), related to the exponential function e x ?

If e x = y , then x = ln( y ) ; ln is used to rearrange capacitor discharge equations to solve for time, t .

True or False? The time constant is the time taken for a capacitor to fully discharge.

False. The time constant is the time taken for the charge, current or p.d. to fall to 37% of its original value, not to fully discharge.

A LevelPhysicsCambridge (CIE)Flashcards19. CapacitanceDischarging a Capacitor

Discharging a Capacitor (Cambridge (CIE) A Level Physics): Flashcards

Exam code: 9702

1/13

0Still learning

Know0

FrontCapacitor Discharge Graphs
Define exponential decay in the context of a discharging capacitor.

Was this flashcard helpful?

Cards in this collection (13)

Define exponential decay in the context of a discharging capacitor.
Exponential decay means the rate at which the current, p.d. or charge decreases is proportional to the amount of current, p.d. or charge remaining.
How does the current behave at the start of a capacitor's discharge, and how does it change over time?
The current is large at the start (in the opposite direction to when it was charging) and gradually falls to zero.
How does increasing the resistance in a discharge circuit affect the rate at which a capacitor discharges?
A higher resistance means the current decreases and charge flows from the plates more slowly, so the capacitor takes longer to discharge (a lower resistance discharges the capacitor faster).
During discharge, in which direction do electrons flow between the capacitor plates?
Electrons flow from the negative plate to the positive plate until there are equal numbers of charge on each plate.
True or False?
During discharge, the current flows in the same direction as it did during charging.
False.
During discharge, the current flows in the opposite direction to the current during charging.
The graphs of current, potential difference and charge against time during capacitor discharge are all .......... in shape.
The graphs of current, potential difference and charge against time during capacitor discharge are all identical in shape.
Define the time constant, $τ$ , of a discharging capacitor.
The time constant is the time taken for the charge, current or potential difference of a discharging capacitor to decrease to 37% (1/e) of its original value.
What is the equation for the time constant, $τ$ , in terms of resistance R and capacitance C?
$τ = R C$
What is the general equation for the exponential decay of a quantity X (current, charge or p.d.) during capacitor discharge?
$X = X_{0} e^{- \frac{t}{R C}}$
where X₀ is the initial value of X before discharge began
What effect does a larger time constant have on the rate of capacitor discharge?
The larger the time constant, the slower the current, charge or p.d. falls during discharge.
How is the natural logarithm, ln(y), related to the exponential function e^x?
If e^x = y, then x = ln(y); ln is used to rearrange capacitor discharge equations to solve for time, t.
The time constant, $τ$ , of a discharging capacitor is measured in units of ...........
The time constant, $τ$ , of a discharging capacitor is measured in units of seconds.
True or False?
The time constant is the time taken for a capacitor to fully discharge.
False.
The time constant is the time taken for the charge, current or p.d. to fall to 37% of its original value, not to fully discharge.

Sign up to unlock flashcards

By signing up you agree to our Terms and Privacy Policy

Previous:Energy Stored in a CapacitorNext:Concept of a Magnetic Field