In standard AC household supply in India, the frequency of the alternating current is 50 Hz. How many times per second does the current change its direction? MCQ with Answer and Explanation
In standard AC household supply in India, the frequency of the alternating current is 50 Hz. How many times per second does the current change its direction?
A. 50 times
B. 100 times
C. 25 times
D. 0 times
Answer: Option B
Solution (By JKSSB Mock Tests)
A frequency of 50 Hz means there are 50 complete wave cycles per second. A single complete sinusoidal cycle consists of one positive half-cycle and one negative half-cycle. Therefore, the current reaches zero and reverses its direction exactly twice during each complete cycle. For 50 cycles, the current changes direction 50 * 2 = 100 times per second.
Explanation:
Circle total resistance 5 Ω. Across diameter, two halves in parallel, each half 2.5 Ω. Parallel: R = (2.5×2.5)/(2.5+2.5) = 6.25/5 = 1.25 Ω. Equal parallel resistors gives half of each.
Explanation:
The area under velocity-time graph gives displacement when direction is considered (signed area), and distance travelled when absolute values are taken (unsigned area). For unidirectional motion, both are equal. Velocity is rate of change of displacement, so integrating velocity over time yields displacement. This graphical interpretation is fundamental in kinematics. Memory tip: Slope of v-t graph = acceleration; area under v-t graph = displacement. Competitive exams often combine graph analysis with conceptual understanding to test depth of knowledge in motion topics.
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