3(iv)
The diagram given below shows a copper wire wound around a U-shape soft iron bar. An iron pin is brought near the arrangement. First Source P and then Source Q are connected across AB, each operating independently.
(a) State True or False: Source P as well as Source Q, when connected across AB, can attract the iron pin.
(b) Justify your answer to (a) with a suitable reason.
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(a) True.
(b) The coil on a soft-iron core acts as an electromagnet with either supply.
- With P (AC): an alternating magnetic field repeatedly magnetises the soft iron; a ferromagnetic pin is attracted in both half-cycles (polarity doesn't matter).
- With Q (DC): a steady field magnetises the core continuously, so the pin is attracted.