Final answer:
The voltage in a circuit varies as current moves through it, and changes in voltage or resistance affect the current according to Ohm's law. Doubling the voltage across a fixed resistance doubles the current; while the power dissipated increases with the square of the current. The behavior of resistors in parallel and capacitors in series or parallel also adheres to these principles.
Step-by-step explanation:
The voltage in a circuit typically varies as current moves through different components that offer resistance. Ohm's law, which states that the current through a conductor between two points is directly proportional to the voltage across the two points, can be applied to understand this behavior. According to Ohm's law, if the resistance is constant and the voltage across it is doubled, the current also doubles. Conversely, if the current is doubled, the power dissipated by the resistor increases by a factor of four, since power is proportional to the square of the current.
If two identical resistors are connected in parallel and the resistance of one resistor is increased, the current through and the voltage across the other resistor remain the same because in parallel circuits, voltage across the resistors is equal and not affected by the change in resistance of one.
When discussing capacitors, adding more capacitors in parallel increases the total capacitance and hence the energy stored in the circuit increases. However, in series, the overall capacitance decreases and the energy stored would thus also decrease.