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JEE · Physics · Alternating Current doubts
8 doubts found
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JEEPhysicshard
Why is electricity sent across the country at very high voltage instead of the 230 V we use at home?
Power lost in the wires is I²R.
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JEEPhysicshard
Why does a capacitor block DC but let AC pass?
A capacitor's opposition is Xc = 1/(ωC).
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JEEPhysicshard
How does tuning a radio pick out just one station from all the signals in the air?
The radio's LCR circuit is set to resonance by adjusting C (or L).
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JEEPhysicshard
Why won't a transformer work on a DC supply?
A transformer works by mutual induction: the changing current in the primary makes a changing magnetic flux that induces a voltage in the secondary.
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JEEPhysicshard
Our mains is '230 V', but I read the peak is about 325 V — which is right?
Both.
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JEEPhysicshard
To dim a light on AC, why is a choke (coil) better than a resistor?
A resistor would limit the current but waste the extra energy as heat.
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JEEPhysicseasy
What does “Reactance” actually mean in Alternating Current, and why does it matter for JEE?
the opposition a capacitor (Xc = 1/ωC) or inductor (XL = ωL) offers to AC — frequency-dependent, unlike resistance.
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JEEPhysicsmedium
I keep getting “Reactance” questions wrong in Alternating Current. What's the trap?
treating reactance as a fixed resistance.
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