Question

As shown in the figure a metal rod makes contact and complete the circuit. The circuit is perpendicular to the magnetic field with B = 0.15 Tesla. If the resistance is 3Ω, force needed to move the rod as indicated with a constant speed of 2m/sec is

• A. 3.75 × 10^–3N
• B. 3.75 × 10^–2N
• C. 3.75 × 10²N
• D. 3.75 × 01^–4N

Answer 1

Answer: (A)

3.75 × 10^–3N

Answer 2

Force needed to move the rod is $F = \frac { B ^ { 2 } v l ^ { 2 } } { R }$

$= \frac{(0.15)^{2} \times 2 \times (0.5)^{2}}{3} = 3.75 \times 10^{- 3}N$