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:

An electromagnet produces a magnetic field as the result of $I$ flow in a conductor.

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

Two small aluminum spheres, each having mass $0.0250$ kg, are separated by $80.0$ cm. How many electrons does each sphere contain? (The atomic mass of aluminum is $26.982$ g/mol, and its atomic number is $13$.)