A 12\,V battery is connected in series with a standard (fixed) resistor of resistance R0 and a second resistor that is drawn with the conventional resistor symbol crossed by a diagonal arrow. Two identical incandescent bulbs, labeled Bulb A and Bulb B, are each connected in parallel with one of the resistors such that
• Bulb A is in parallel with the fixed resistor R0.
• Bulb B is in parallel with the adjustable resistor.
Assume the bulbs are identical, the leads have negligible resistance, and conventional current is used throughout.
(a) Identify the component that can be adjusted in this circuit and cite the schematic feature that reveals its variable nature.
(b) Suppose the resistance of the adjustable component is increased slowly while all other elements remain unchanged. Describe qualitatively how the brightness of Bulb A and Bulb B will change, if at all. Justify your answer with reference to current paths and potential differences rather than numerical calculations.
(c) Explain qualitatively how the rate of energy dissipation (power) in the adjustable component changes as its resistance is increased. Your answer should discuss both the current through that branch and the potential difference across it.