The maximum kinetic energy of protons in a cyclotron of radius $0.4 \mathrm{m}$ in a magnetic field of $0.5 \mathrm{T}$ is (mass of proton $=1.67 \times 10^{-27} \mathrm{kg}$, charge of proton $\left.=1.6 \times 10^{-19} \mathrm{C}\right)$

The ratio of the magnetic field at the centre of a current carrying circular wire and the magnetic field at the centre of a semi-circular coil made from the same length of wire will be

Two infinite length wires carry currents $8 \mathrm{A}$ and $6 \mathrm{A}$ and are placed along $X$ -axis and Y-axis respectively. Magnetic field at a point $\mathrm{P}(0,0, \mathrm{d}) \mathrm{m}$ will be

In an ammeter, $4 \%$ of the main current is passing through the galvanometer. If shunt resistance is $5 \Omega,$ then resistance of galvanometer will be

Assertion: In a shunted galvanometer, only $10 \%$ current passes through the galvanometer. The resistance of the galvanometer is $G$. Then the resistance of the shunt is $\frac{G}{9}$.

Reason: If $\mathrm{S}$ is the resistance of the shunt, then voltage across $S$ and $G$ is same.

Two wires with currents $2 \mathrm{A}$ and $1 \mathrm{A}$ are enclosed in a circular loop. Another wire with current $3 \mathrm{A}$ is situated outside the loop as shown. The $\oint \overrightarrow{\mathrm{B}} \cdot \overrightarrow{\mathrm{d} l}$ around the loop is

A vertical straight conductor carries a current vertically upwards. A point $P$ lies to the east of it at a small distance and another point $Q$ lies to the west at the same distance. The magnetic field at $P$ is