Question

Assertion: AC is more dangerous than DC
Reason: Frequency of ac is dangerous for human beings
(A) Both the Assertion and the Reason are correct.
(B) Both the statements are correct and Reason is the correct explanation of the Assertion.
(C) Both the statements are correct and Reason is not the correct explanation of the Assertion.
(D) Both the Assertion and the Reason are incorrect.

Answer 1

Frequency$f$ in a dc current is always zero while in ac current, it is generally 50 Hz or 60 Hz. Alternating current is a type of electrical current whose direction of flow of electrons switches back and forth at regular intervals, whereas direct currents are unidirectional.

Complete step by step answer:
When a current passes through a human body, then body acts as a capacitance between the current-carrying conductor and the earth surface since there is no loopback between the earth surface and the conductor
We know capacitance is given as${X_C} = \dfrac{1}{{\omega C}} = \dfrac{1}{{2\pi fC}} - - (i)$, where f is the frequency of the current passing through the body, and it is inversely proportional to the reactive capacitance${X_C} \propto \dfrac{1}{f}$.
Now in the case of DC currents, we know the frequency$f = 0$, so the reactive capacitance in the body becomes

$$\Rightarrow {X_C} = \dfrac{1}{{2\pi fC}} \\\ \Rightarrow {X_C} = \dfrac{1}{{2\pi \times 0 \times C}} \\\ \therefore {X_C} = \infty \\\$$

Hence we can say reactive capacitance becomes infinite, which means the body will provide high resistance to the flow of current due to which human beings do not feel shocked.
Now in the case of AC currents, we know frequency is generally 50 Hz or 60 Hz, so the reactive capacitance decreases in the body
${X_C} \downarrow \propto \dfrac{1}{{f \uparrow }}$
This means opposition to the flow of current through the body also decreases due to which current starts to flow; hence we can say in the case of AC current, we will feel shocked.
Therefore both the Assertion and the Reason are correct and Reason is the correct explanation of the Assertion.

Hence,option(B) is correct.

Note: Students must note that at the same voltage level of ac and dc current to cause more severe damages, more milliamps dc currents are required. AC current causes muscle, contraction and sweating.