The circuit diagram shows a resistor and a thermistor connected in series with a 6 V battery - Leaving Cert Physics - Question d - 2014

The total resistance (R_total) in a series circuit is the sum of individual resistances. Here, we have:

• 50 Ω (resistor)
• 450 Ω (thermistor)

Thus, the total resistance is: $R_{total} = 50 \, ext{Ω} + 450 \, ext{Ω} = 500 \, ext{Ω}$

Using Ohm's law, we can find the current (I) using the total voltage (V) and the total resistance (R_total):

$I = \frac{V}{R_{total}} = \frac{6 \, V}{500 \, ext{Ω}} = 0.012 \, A = 12 \, mA$

The potential difference (V) across the 50 Ω resistor can be calculated using Ohm's law:

$V = I \times R = 0.012 \, A \times 50 \, ext{Ω} = 0.6 \, V$

If the temperature were increased, the resistance of the thermistor would typically decrease, leading to a decrease in the total resistance of the circuit. This change is dependent on the type of thermistor used (NTC or PTC).