A wire shown in figure Fig. $8.116$ carries a current of $40 \mathrm{A}$. If $r=3.14 \mathrm{cm}$, the magnetic field at the point $P$ will be

 

 

Two long parallel conductors carry currents in opposite directions as shown in Fig. $8.117$. One conductor carries a current of $10 \mathrm{A}$ and the distance between the wires is $d=10 \mathrm{cm}$ Current $I$ is adjusted, so that the magnetic field at $P$ is zero. $P$ is at a distance of $5 \mathrm{cm}$ to the right of the $10 \mathrm{A}$ current. Value of $I$ is 

A wire oriented in the east-west direction carries a current eastward. Direction of the magnetic field at a point to the south of the wire is

In the adjacent figure, Fig.$8.118,$ is shown a closed path $P$. A long straight conductor carrying a current $I$ Passes through $O$ and perpendicular to the plane of the paper. Then which of the following holds good ?

A cell is connected between the points $A$ and $C$ of a circular conductor $ABCD$ with $O$ as centre Fig. $8.119$ and angle $AOC=60°.$ If $B_1$ and $B_2$ are the magnitudes of the magnetic fields at $O$ due to the currents in $ABC$ and $ADC$ respectively, then ratio $\frac{B_1}{B_2}$ is