Two very long, straight, parallel wires $A$ and $B$ carry currents of $10 A$ and $20 A$ respectively and are at a distance $20 \mathrm{cm}$ apart, as shown in Figure. lf a third wire $C$ (length $15 \mathrm{cm}$) having a current of $10 A$ is placed between them, how much force, will act on $C$? The direction of current in all the three wires is same.

In Figure, $ABCD$ is a rectangular loop made of uniform wire. The length $AD=BC=1 \mathrm{cm}$. The sides $AB$ and $DC$ are much longer than $AD$ or $BC$. Find the magnetic force per unit length acting on the wire $DC$ due to the wire $AB$ if the ammeter reads $10 A$.

A rectangular loop of wire of size $2 \mathrm{cm}\times 5 \mathrm{cm}$ carries a steady current of $1 A$. A straight long wire carrying $4 A$ current is kept near the loop as shown in Figure. If the loop and the wire are coplanar, find (i) the torque acting on the loop and (ii) the magnitude and direction of the force on the loop due to the current carrying wire.

A square loop of side $20 \mathrm{cm}$ carrying current of $1 A$ is kept near an infinite long straight wire carrying a current of $2 A$ in the same plane as shown in Figure. Calculate the magnitude and direction of the net force exerted on the loop due to the current carrying conductor.

A rectangular coil $PQRS$ is placed in a uniform magnetic field $\overrightarrow{B}$, as shown in Figure. Find the torque on the coil when it carries a current of $2.0 A$. The magnitude of the field $\overrightarrow{B}$ is $2.0\times {10}^{-2} T$.

A galvanometer has a resistance of $8 \mathrm{\Omega }$. It gives a full-scale deflection for a current of $10 mA$. It is to be converted into an ammeter of range $5 A$. The only shunt resistance available is of $0.02 \mathrm{\Omega }$, which is not suitable for this conversion. Find the value of resistance $R$ that must be connected in series with the galvanometer (Figure) to get ammeter of desired range.

The circuit shown in Figure is used to measure the resistance $R$. The ammeter reads $0.13 A$ and the voltmeter reads $117 V$. The resistance of the ammeter is $0.015 \mathrm{\Omega }$ and that of the voltmeter is $9000 \mathrm{\Omega }$. Find the value of $R$.