If a wire carries a current $i$ into a junction, and two wires carry currents $i_1$ and $i_2$ away from the junction, which equation correctly expresses the conservation of electric charge at the junction?

A typical lemon battery can be made by inserting a zinc nail and a copper coin into a lemon. Estimate the electric current ($I$, in amperes) that such a lemon battery can deliver under normal conditions.

In the circuit shown in (figure 1), a capacitor is connected in series with a resistor and a battery. The switch has been closed for a long time prior to $t=0$, allowing the circuit to reach steady state. What is the charge stored on the capacitor just before $t=0$?

In a simple circuit consisting of a battery of emf $E$ and an external resistor $R$, the battery current $i$ is:

Two point charges are fixed on the y-axis at positions $(0,a)$ and $(0,-a)$. If both charges have magnitude $q$ but opposite signs, what is the direction of the electric field at the origin?

How many electrons make up −1.5 × 10⁻⁵ C?

How many electrons do you have to add to decrease the charge of an object by 16 μC?