A tuning fork produces 4 beats per second when sounded with a 256 Hz standard fork. When a little wax is attached to the tuning fork, the beat frequency drops to 2 beats per second. The original frequency of the tuning fork was: MCQ with Answer and Explanation
A tuning fork produces 4 beats per second when sounded with a 256 Hz standard fork. When a little wax is attached to the tuning fork, the beat frequency drops to 2 beats per second. The original frequency of the tuning fork was:
A. 258 Hz
B. 254 Hz
C. 252 Hz
D. 260 Hz
Answer: Option D
Solution (By JKSSB Mock Tests)
Beat frequency is the absolute difference between two frequencies. Given 4 beats with 256 Hz, the unknown fork is either 256+4=260 Hz or 256-4=252 Hz. Adding wax increases mass, which strictly lowers the frequency of a fork. If it was 252 Hz, lowering it would increase the gap from 256, increasing beats. If it was 260 Hz, lowering it brings it closer to 256, decreasing beats to 2. Thus, it was originally 260 Hz.
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?
Explanation:
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.
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