Question

The inner and outer radius of a toroid core are 28 cm and 29 cm respectively and around the core 3700 turns of a wire are wounded. If the current in the wire is 10 A, then the magnetic field inside the core of the toroid is
A. `2.60 xx 10^(-2)T`
B. `2.60 xx 10^(-3)T`
C. `4.52 xx 10^(-2)T`
D. `4.52 xx 10^(-3)T`

Answer 1

Correct Answer - A
The number of turns per unit length for the given toroid `n=(N)/(2pir_("av"))`
The average radius of toroid
`r_("av")=(28+29)/(2)="28.5 cm "=28.5xx10^(-2)m`
`therefore" "n=(3700)/(2xx3.14xx28.5xx10^(-2))=2067.27~~2067`
Now, `B=mu_(0)nI=4pixx10^(-7)xx2067xx10`
`=2259615.2xx10^(-7)T=2.60xx10^(-2)T`