MHT CET · Physics · Electromagnetic Induction
A coil of self inductance \(L\) is connected in series with a bulb B and an a.c. source. Brightness of the bulb decreases when
- A frequency of a.c. source is decreased.
- B number of turns in the coil is reduced.
- C a capacitance of reactance \(\left(X_L-X_C\right)\) is included in the same circuit.
- D an iron rod is inserted in the coil.
Answer & Solution
Correct Answer
(D) an iron rod is inserted in the coil.
Step-by-step Solution
Detailed explanation
When iron rod is inserted, the coil magnetizes the iron rod increasing the magnetic field.
\(\therefore \quad\) Inductance (L) of coil increases.
\(\mathrm{V}=\mathrm{L} \frac{\mathrm{di}}{\mathrm{dt}}\)
\(\therefore \quad\) Voltage drop across the coil increases i.e. voltage drop at bulb decreases.
\(\therefore \quad\) Brightness of bulb decreases.
\(\therefore \quad\) Inductance (L) of coil increases.
\(\mathrm{V}=\mathrm{L} \frac{\mathrm{di}}{\mathrm{dt}}\)
\(\therefore \quad\) Voltage drop across the coil increases i.e. voltage drop at bulb decreases.
\(\therefore \quad\) Brightness of bulb decreases.
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