Two long parallel wires carry equal currents in opposite directions. What field do the two wires produce at point M, which is midway between the wires and on the plane of the paper?

In the circuit in the diagram, the ammeter reads 7.0A. Determine the unknown emf $\epsilon$.

Describe the energy changes taking place in the circuit shown in the diagram.

Calculate the current in, and potential difference across, the resistor in the circuit shown in the diagram.

A student assigns currents at a junction in a circuit as shown in the diagram.

The student's calculations correctly give that $I_1=3 \mathrm{A}$ and  $I_2=-2 \mathrm{A}$. The value of $I_3$ is: