A capacitor of 2 µF is connected as shown in circuit. The internal resistance of the battery is 1 Ω. The amount of charge on the capacitor in steady state will be?

Question image

Understand the Problem

The question is asking to determine the charge on a capacitor in a given electrical circuit, factoring in the internal resistance of the battery. This involves understanding how capacitors function in circuits and applying relevant formulas to find the charge.

Answer

The charge on the capacitor is approximately $10 \, \mu C$.
Answer for screen readers

The charge on the capacitor in steady state will be approximately $10 , \mu C$.

Steps to Solve

  1. Identify the circuit and components

In the given circuit, we have a capacitor, resistors, and a battery. The capacitor value is $2 , \mu F$ and the resistors are $5 , \Omega$ and $2 , \Omega$ with an internal resistance of $1 , \Omega$. The effective resistance in series with the capacitor can be calculated as:
$$ R_{total} = 5 , \Omega + 2 , \Omega + 1 , \Omega = 8 , \Omega $$

  1. Calculate the total current in the circuit

Using Ohm's law, the current $I$ flowing through the circuit can be calculated by:
$$ I = \frac{V}{R_{total}} = \frac{6 , V}{8 , \Omega} = 0.75 , A $$

  1. Determine the voltage across the capacitor

Since the capacitor is in steady state, the voltage across it can be found using the formula for charge on a capacitor:
$$ V_C = I \times R_{equiv} $$
Where $R_{equiv}$ is the total resistance in series with the capacitor. We can find this by taking the total voltage drop across resistors. The total resistance is $8 , \Omega$, hence:
$$ V_C = I \times (2 , \Omega + 5 , \Omega) = 0.75 , A \times 7 , \Omega = 5.25 , V $$

  1. Calculate the charge on the capacitor

Now, using the capacitance formula: $$ Q = C \times V_C $$
Where ( C = 2 , \mu F ), we convert capacitance to farads: ( 2 , \mu F = 2 \times 10^{-6} F ). So:
$$ Q = 2 \times 10^{-6} F \times 5.25 , V = 10.5 \times 10^{-6} , C = 10.5 , \mu C $$

  1. Final approximation and values

Since the options provided are discrete values, we need to round to the closest presented answer, which is $10 , \mu C$.

The charge on the capacitor in steady state will be approximately $10 , \mu C$.

More Information

In capacitive circuits, the charge stored is dependent on both the voltage across the capacitor and its capacitance. The effective resistance in series impacts the current flowing which can change the steady-state voltage across the capacitor.

Tips

  • Miscalculating the total effective resistance. It's important to note all resistances in series when finding total resistance.
  • Not converting units correctly, especially for capacitance and the final charge.
  • Forgetting to consider the voltage drop across resistors in series before calculating the charge on the capacitor.
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