• November 21, 2021

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• PHY102 Physics II © Dr.Cem Özdoğan

• 28-9 Torque on a Current Loop

• The elements of an electric motor

• The elements of an electric motor:
• A rectangular loop of wire, carrying a current and free to rotate about a fixed axis, is placed in a magnetic field.
• Magnetic forces on the wire produce a torque that rotates it.
• The two magnetic forces F and –F produce a torque on the loop, tending to rotate it about its central axis.
• A commutator (not shown) reverses the direction of the current every half-revolution so that the torque always acts in the same direction (FYI).

• Magnitude of the total torque on the coil (of area A and N turns):

FB=ibBsinφ , φ=90

τ=rFB=aibBsinθ

τ=(iA)B=μB

μ:magnetic moment