Motional Emf: a Conducting Bar Slides Without Friction on Two

question 63

Multiple Choice

Motional emf: A conducting bar slides without friction on two parallel horizontal rails that are 50 cm apart and connected by a wire at one end. The resistance of the bar and the rails is constant and equal to 0.10 Ω. A uniform magnetic field is perpendicular to the plane of the rails. A 0.080-N force parallel to the rails is required to keep the bar moving at a constant speed of 0.50 m/s. What is the magnitude of the magnetic field?

• A) 0.10 T
• B) 0.25 T
• C) 0.36 T
• D) 0.54 T
• E) 0.93 T

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Definitions:

Caldera

A large, cauldron-like depression that forms following the eruption and collapse of a magma chamber beneath a volcano.

Platinum

A dense, malleable, ductile, and highly unreactive precious metal used in jewelry, automotive catalytic converters, and various industrial applications.

Mafic to Ultramafic Intrusions

The intrusion of magma rocks ranging from mafic (rich in magnesium and iron) to ultramafic (extremely rich in magnesium and iron) compositions, important in the formation of various ore deposits.

Veins

Mineral deposits that fill cracks in rocks, often distinguished by their different materials from the surrounding rock.