1) Immediately after the battery is connected, what is the voltage across the re

Question

1)  Immediately after the battery is connected, what is the voltage across the resistor? How do you know?

2)  What is the resistance of the resistor? How do you know?

3)  After the battery has been connected for a long time, what is the voltage across the capacitor? How do you know?

4)  Immediately after the battery is disconnected, what is the voltage across the resistor? How do you know?

5)  Immediately after the battery is disconnected, what is the voltage across the capacitor? How do you know?

6)  After the battery has been disconnected for a long time, what is the voltage across the resistor? How do you know?

7) The time constant for an RC circuit is the amount of time it takes the capacitor to gain 63.2% of its charge (charging) or lose 63.2% of its charge (discharging). It is also equal to the time it takes the current to fall by 63.2% in an RC circuit. Using this information, find the value for C, the capacitance of the capacitor? How do you know?

Explanation / Answer

1)

as the battery is connected , there is no charge stored in the capacitor. hence there is no voltage across the capacitor and hence all the voltage appear across the resistor

Voltage across the resistor = battery Voltage

2)

from the graph , i = current when battery is connected = 20 A

so resistance = battery voltage / current = V/20

3)

After the battery is connected for the long time , the capacitor gets fully charges and flow of current in the circuit stops. therefore there is no voltage across the resistor and all the voltage appear across the capacitor

4)

immediately after the battery is disconnected , the voltage across the resistor is same as the voltage across the capacitor. the capacitor starts discharging due to which current starts flowing in the circuit. this current is given as

i = V/R

R = V/20

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