Two circular coils $1$ and $2$ are made from the same wire but the radius of the $1^{st}$ coil is twice that of the $2^{nd}$ coil. What is the ratio of potential difference in volts should be applied across them so that the magnetic field at their centres is the same?
$2$
$3$
$4$
$6$
A coil having $N$ turns is wound tightly in the form of a spiral with inner and outer radii $a$ and $b$ respectively. When a current $i$ passes through the coil, the magnetic field at the centre is
The magnetic field intensity at the point $O$ of a loop with current $i$, whose shape is illustrated below is
Two concentric coils each of radius equal to $2\pi \,{\rm{ }}cm$ are placed at right angles to each other. $3$ $ampere$ and $4$ $ampere$ are the currents flowing in each coil respectively. The magnetic induction in $Weber/{m^2}$ at the centre of the coils will be $({\mu _0} = 4\pi \times {10^{ - 7}}\,Wb/A.m)$
Write formula for magnetic field due to a circular current carrying loop having $\mathrm{N}$ turns and $\mathrm{R}$ radius at a point on the axis of the loop.
When the current flowing in a circular coil is doubled and the number of turns of the coil in it is halved, the magnetic field at its centre will become