Thermistor's negative temperature coefficient causes voltage to rise nonlinearly with current

Steps:

• Current through thermistor increases, causing it to heat up due to power dissipation (V*I).
• Heating raises temperature, decreasing resistance R for an NTC thermistor.
• Voltage V = I * R; as I rises, R falls, so V increases but at a decreasing rate.
• Graph of V vs. I shows a curve starting steep and flattening, not linear.

Why A is correct:

• Matches V = I R where R decreases with rising I, producing a concave-down curve per Ohm's law adapted for temperature dependence.

Why the others are wrong:

• B: Linear increase assumes constant R, ignoring heating effect.
• C: Voltage decrease contradicts V = I R with positive I and R.
• D: Steep or exponential rise implies increasing R, opposite of NTC behavior.

Final answer: A