| ASSERTION: A loosely round helix made of stiff wire is suspended vertically with the lower end just touching a dish of mercury. When a current is passed through the wire, the helical wire executes oscillatory motion with the lower end jumping out of and into the mercury. |
| REASON: When electric current is passed through helix, a magnetic field is produced both inside and outside the helix. |
A) If both assertion and reason are true and reason is the correct explanation of assertion.
B) If both assertion and reason are true and reason is not the correct explanation of assertion.
C) If assertion is true but reason is false.
D) If both assertion and reason are false.
E) If assertion is false but reason is true.
Correct Answer: B
Solution :
The winding of helix carry current in same direction therefore they experience an attractive force pulling the lower end out of mercury. As a result of this, the circuit breaks. Current becomes zero and hence the force of attraction vanishes. Therefore helix comes back to its initial position, completing the circuit again. In this way the process is repeated and the helix executes oscillatory motion.
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