A student sets up the circuit shown below to monitor temperature changes in an incubator. The circuit consists of a 6.0 V power supply of negligible internal resistance, a fixed resistor of resistance 3.0 kΩ3.0\text{ k}\Omega3.0 kΩ, and a negative temperature coefficient (NTC) thermistor.
Initially, the reading on the voltmeter connected across the thermistor is 4.0 V.
The temperature of the incubator is then increased, causing the resistance of the thermistor to decrease to 25% of its initial value.
What is the new potential difference across the fixed resistor?
2.0 V2.0\text{ V}2.0 V
4.0 V4.0\text{ V}4.0 V
4.5 V4.5\text{ V}4.5 V
5.0 V5.0\text{ V}5.0 V