Magnetic Effects Of Current Question 12
Question 12 - 2024 (31 Jan Shift 1)
A coil is placed perpendicular to a magnetic field of $5000 T$. When the field is changed to $3000 T$ in $2 s$, an induced emf of $22 V$ is produced in the coil. If the diameter of the coil is $0.02 m$, then the number of turns in the coil is :
(1) 7
(2) 70
(3) 35
(4) 140
Show Answer
Answer: (2)
Solution:
$\varepsilon=N\left(\frac{\Delta \phi}{t}\right)$
$\Delta \phi=(\Delta B) A$
$B _i=5000 T$,
$B _f=3000 T$
$d=0.02 m$
$r=0.01 m$
$\Delta \phi=(\Delta B) A$
$=(2000) \pi(0.01)^{2}=0.2 \pi$
$\varepsilon=N\left(\frac{\Delta \phi}{t}\right) \Rightarrow 22=N\left(\frac{0.2 \pi}{2}\right)$
$N=70$
