Directions : In the following questions, A statement of Assertion (A)...
Capacitive reactance = 1/2πfC
So, as f (frequency) increases, reactance decreases. For dc, frequency = 0, hence capacitor offers infinite reactance. So, it blocks dc. For ac, frequency ≠ 0,hence capacitor offers low reactance and allows ac to pass. Hence assertion and reason both are true. Assertion is properly explained by reason.
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Directions : In the following questions, A statement of Assertion (A)...
Assertion (A): Capacitor blocks dc and allows ac to pass.
Reason (R): Capacitive reactance is inversely proportional to frequency.
The correct answer is option 'A', which means that both the assertion and the reason are true, and the reason is the correct explanation of the assertion.
Explanation:
Capacitor Blocks DC and Allows AC to Pass:
A capacitor is a passive electronic component that stores and releases electrical energy. It consists of two conductive plates separated by an insulating material known as the dielectric. When a direct current (DC) voltage is applied across the capacitor, it charges up and blocks the flow of current after it becomes fully charged. This is because the dielectric material does not allow the flow of direct current. Therefore, a capacitor blocks DC and does not allow it to pass through.
On the other hand, when an alternating current (AC) voltage is applied across the capacitor, the capacitor charges and discharges at each cycle of the AC signal. The charging and discharging of the capacitor allow the AC signal to pass through. This is why capacitors are commonly used in AC circuits for various applications such as coupling, filtering, and energy storage.
Capacitive Reactance and Frequency:
Capacitive reactance is the opposition offered by a capacitor to the flow of alternating current. It is denoted by Xc and is inversely proportional to the frequency of the AC signal. The formula for capacitive reactance is given by:
Xc = 1/(2πfC)
Where:
Xc = Capacitive reactance
f = Frequency of the AC signal
C = Capacitance of the capacitor
From the formula, it is evident that as the frequency of the AC signal increases, the capacitive reactance decreases. This means that a higher frequency AC signal will encounter less opposition from the capacitor and allow more current to pass through. Conversely, a lower frequency AC signal will encounter higher capacitive reactance, resulting in less current passing through.
Conclusion:
The assertion states that a capacitor blocks DC and allows AC to pass, which is true. The reason provided for this assertion is also true. Capacitive reactance is indeed inversely proportional to the frequency of the AC signal. As the frequency increases, the capacitive reactance decreases, allowing more current to pass through the capacitor. This explains why capacitors are effective in blocking DC and allowing AC to pass through. Therefore, both the assertion and the reason are true, and the reason correctly explains the assertion.