Question

A coil of mean area 500 $c{m}^2$ and having 1000 turns is held perpendicular to a uniform field of 0.4 gauss. The coil is turned through ${180}^o$ in $\frac{1}{10}$ second. The average induced w.m.f. :-

• A. 0.04 V
• B. 0.4 V
• C. 4 V
• D. 0.004 V

Answer 1

The correct option is A 0.04 V

Given, $A=500c{m}^2=500\times 10⁻⁴=0.05m^2$

Number of turns$=N=1000$

Magnetic field $=B=0.4G=0.4\times 10⁻⁴T$

∆t = time taken$=1/10=0.1$ sec

Coil turned $\theta =0^0$ to$\theta ={180}^0$ as shown in figure.

Change in flux =

so, change in flux =$\Delta \Phi =-2NBA$

We know,

Where Eav is average induced emf

So, $Eav=2NBA/\Delta$t

=$2\times 1000\times 0.4\times 10⁻⁴\times 0.05/0.1$

$=0.04V$