A circuit contains two resistors in series connected to an ideal battery: • at
PHYSICS · Single correct · CBSE · Physics · Current Electricity · Current Electricity
Problem
A circuit contains two resistors in series connected to an ideal battery:
• Rmetal=100Ω at 25∘C, made of a typical metal whose resistance increases with temperature.
• Rtherm=100Ω at 25∘C, made of a material whose resistance decreases with temperature.
When the circuit operates, both resistors reach 35∘C. At this temperature, Rmetal has increased by 5%, and Rtherm has decreased by 10%. Which statement best describes what happens to the magnitude of the current after the temperature rise?
(a) The current decreases because the metal resistor’s 5% increase in resistance makes the total resistance larger.
(b) The current is essentially unchanged because the two equal-but-opposite percentage changes offset one another.
(c) The current increases slightly because the total series resistance becomes smaller (about 2.5% lower).
(d) The current increases by about 10% because the thermistor’s larger percentage decrease in resistance dominates the circuit.