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Question : 16
Total: 26
(i) When an AC source is connected to an ideal inductor show that the average power supplied by the source over a complete cycle is zero.
(ii) A lamp is connected in series with an inductor and an AC source. What happens to the brightness of the lamp when the key is plugged in and an iron rod is inserted inside the inductor? Explain.
(ii) A lamp is connected in series with an inductor and an AC source. What happens to the brightness of the lamp when the key is plugged in and an iron rod is inserted inside the inductor? Explain.
Solution:
Proof for average power
Effect on brightness
Explanation
(i)P a v = I a v × e a v cos ϕ
For an ideal inductor,ϕ =
∴ P a v = I a v × e a v cos
P a v = 0
(ii) Brightness decreases
Because as iron rod is inserted inductance increases.
Thus, current decreases and brightness decreases.
Effect on brightness
Explanation
(i)
For an ideal inductor,
(ii) Brightness decreases
Because as iron rod is inserted inductance increases.
Thus, current decreases and brightness decreases.
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