Given below are two statements: one is labelled as Assertion (A) and the other is labelled as Reason (R). In the light of the above statements, choose the most appropriate answer from the options given below :
- (A) is true but (R) is false
- Both (A) and (R) are true and (R) is the correct explanation of (A).
- Both (A) and (R) are true but (R) is not the correct explanation of (A)
- (A) is false but (R) is true
Answer
(2) Both (A) and (R) are true and (R) is the correct explanation of (A).
Solution
(A): A choke coil has large inductance and small resistance. Connected directly to the mains, the tube would draw a very large current and be damaged; the choke limits the current. So (A) is true.
(R): Tube (resistance R) in series with the choke (inductance L):
I = V R2 + 2L2 VR = IR = V R R2 + 2L2
So the voltage across the tube is reduced by the factor R R2 + 2L2; without the choke, VR = V. So (R) is true.
Since the choke reduces the voltage (and current) through the tube without wasting much power, (R) correctly explains why the tube is not damaged.
Answer: (2)