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Questions and Answers
What is the necessary area of the plates of a parallel plate capacitor to achieve a capacity of 1.0 F with a plate separation of 50 µm?
What is the necessary area of the plates of a parallel plate capacitor to achieve a capacity of 1.0 F with a plate separation of 50 µm?
- 0.78 m²
- 1.39 m²
- 0.38 m²
- 2.52 m² (correct)
What decay law describes the current in the Goldcap over time during discharging?
What decay law describes the current in the Goldcap over time during discharging?
- Logarithmic decay law
- Quadratic decay law
- Linear decay law
- Exponential decay law (correct)
How can the internal resistance of the Goldcap be determined from the current measurements during discharging?
How can the internal resistance of the Goldcap be determined from the current measurements during discharging?
- By using the current values to calculate total resistance
- By plotting the current against time and finding the slope
- Using Ohm's law with the voltage and current measurements (correct)
- By averaging the current values
What will happen to the voltage in the data storage device after a power failure given an initial voltage of 5.0 V and a resistance of 4.8 MΩ?
What will happen to the voltage in the data storage device after a power failure given an initial voltage of 5.0 V and a resistance of 4.8 MΩ?
If the internal resistance of the ammeter is neglected, what equation confirms the relationship for the decay constant k?
If the internal resistance of the ammeter is neglected, what equation confirms the relationship for the decay constant k?
Flashcards
Capacitor Capacity
Capacitor Capacity
The ability of a capacitor to store electrical energy.
Exponential Decay
Exponential Decay
A decrease in a quantity over time following an exponential function where the rate of change is proportional to the remaining amount of the quantity.
Time Constant (τ)
Time Constant (τ)
The time it takes for a quantity to decrease to 1/e (approximately 0.368) of its original value in an exponential decay process.
RC Circuit Discharge
RC Circuit Discharge
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Effective Resistance
Effective Resistance
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Study Notes
Capacitor Properties
- A "Goldcap" is a capacitor with high capacity, smaller than foil capacitors.
- A specific type has a 1.0 F capacitance and a 21 mm diameter, 10 mm height.
Capacitor Plate Area Calculation
- To calculate the required plate area (A) for a 1.0F capacitor with a 50µm separation, use the formula and the permittivity of free space (vacuum).
- The calculation uses the dielectric constant of vacuum (ε₀) in the formula.
Capacitor Discharge and Measurement
- When fully charged, the Goldcap has a voltage (U₀) of 4.5V.
- The discharge occurs across a resistor (Rₐ) with a value of 60Ω.
- A table of measured current (I) values over time (t) is provided.
Current-Time (t-I) Diagram
- The provided time-current data points should create a graph (t-I).
- Analyze this graph to show that the goldcap internal resistance (R₁) is approximately 58Ω.
- The internal resistance of the ammeter is negligible.
Time-ln(I) Diagram
- A graph must be created showing ln(I) vs t (time)
- This graph allows to demonstrate the exponential equation I(t) = I₀ * e^(-kt) by visually checking for a straight line.
- The slope from the trendline of the graph equals -k/R-equivalent(series combination).
Capacitor as Buffer for Electronic Data Storage
- The Goldcap (with 1.0 F capacitance) acts as a buffer during power outage for a data storage device.
- The initial voltage (5.0V), data storage resistor ( R = 4.8MΩ) are key parameters for calculations.
Voltage Decay Calculation
- Determine how long it takes for the voltage to drop to 3.5V after the power outage.
- Disregarding Goldcap's internal resistance, you can use the capacitor discharge equation.
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