Question

What is the value of $R_1$ ?

• A. 0.9 ohm
• B. 1.2 ohm
• C. 0.68 ohm
• D. 0.47 ohm

Answer 1

Answer: (D)

$B_4=0.6T$

$P_1=0.76W$

$P_2=1.2W$

$m=0.2kg$ (of rod)

$P=f\times v=\frac{B^2{l}^2{v}^2}{R}$

$P_1=\frac{B_1^2{l}^2{v}^2}{R_1}$

$R_1=\frac{B^2{l}^2{v}^2}{R_1}$ Since terminal velocity is reached thus $v=1$

$=\frac{(0.6{)}^2\times l^2\times v^2}{\left(0.76\right)}$

$R_1=\frac{0.36}{0.76}=0.47\Omega$